Document:

EX-10.14

 Exhibit 10.14 

11099 NORTH TORREY PINES ROAD 

LEASE 
 This Lease
(this “Lease”), dated as of the date set forth in Section 1 of the Summary of Basic Lease Information (the “Summary”), below, is made by and between HCP TORREY PINES, LLC, a Delaware
limited liability company (“Landlord”), and SYNTHORX INC., a Delaware corporation (“Tenant”). 

SUMMARY OF BASIC LEASE INFORMATION 
  

			
	TERMS OF LEASE	  	DESCRIPTION
		
	1.     Date:	  	September 21, 2018
		
	2.     Premises (Article 1).	  	
		
	 2.1 Building:
	  	That certain two (2)-story building located at 11099 North Torrey Pines Road, San Diego, California 92037, containing a total of 92,479 rentable square feet.
		
	 2.2 Premises:
	  	Approximately 6,905 rentable square feet of space located on the first (1st) floor of the Building and commonly known as Suite 190, as further set forth in Exhibit A to this Lease.
		
	3.     Lease Term (Article 2).	  	
		
	 3.1 Length of Term:
	  	Approximately four (4) years and four (4) months.
		
	 3.2 Lease Commencement Date:
	  	The earlier to occur of (i) the date upon which Tenant first commences to conduct business in the Premises, and (ii) the later to occur of (A) November 1, 2018 and (B) the date upon which the Premises are
Ready for Occupancy (as that term is defined in Section 5.1 of the Tenant Work Letter attached hereto as Exhibit B (the “Tenant Work Letter”)).
		
	 3.3 Lease Expiration Date:
	  	If the Lease Commencement Date shall be the first day of a calendar month, then the day immediately preceding the fifty-second (52nd) month anniversary of the Lease Commencement
Date; or, if the Lease Commencement Date shall be other than the first day of a calendar month, then the last day of the month in which the fifty-second (52nd) month anniversary of the Lease
Commencement Date occurs.

 HCP TORREY PINES, LLC 

[11099 NORTH TORREY PINES ROAD] 

[Synthorx Inc.] 
  

  

													
	 4.  Base Rent (Article 3):
	    
	  			
				
	 Lease Year
	  	Annual
Base Rent	 	  	Monthly
Installment
of Base Rent	 	  	Approximate
Monthly Base
Rent per Rentable
Square Foot*	 
	 Lease Year 1**
	  	$	314,868.00	 	  	$	26,239.00	 	  	$	3.80	 
	 Lease Year 2
	  	$	324,314.04	 	  	$	27,026.17	 	  	$	3.91	 
	 Lease Year 3
	  	$	334,043.52	 	  	$	27,836.96	 	  	$	4.03	 
	 Lease Year 4
	  	$	344,064.82	 	  	$	28,672.06	 	  	$	4.15	 
	 Lease Year 5 (4 months)
	  	$	354,386.76	 	  	$	29,532.23	 	  	$	4.28	 
	
	OPTION TERM (IF APPLICABLE)	  

				
	 Lease Year 1 of Option Term
	  	$	368,562.12	 	  	$	30,713.51	 	  	$	4.45	 

  

	*	 The calculation of the Monthly Base Rent per Rentable Square Foot reflects an annual increase of 3%, rounded to
the nearest cent, after the previous Lease Year; provided, however, that the calculation of the Monthly Base Rent per Rentable Square Foot for the Option Term (if applicable) reflects an annual increase of 4%, rounded to the nearest cent, after the
previous Lease Year. 

	**	 Tenant’s obligation to pay Monthly Installment of Base Rent for the first four (4) full calendar months of
the Lease Term shall be subject to the terms of Section 3.2 of the Lease. 

  

							
	 5.     Tenant Improvements (Exhibit B):
	  	Tenant Improvements to be constructed on a turn-key basis pursuant to the Tenant Work Letter.
		
	6.     Tenant’s Share (Article 4):	  	7.4666%.
		
	7.     Permitted Use (Article 5):	  	The Premises shall be used only for general office, research and development and laboratory uses, including, but not limited to, administrative offices and other lawful uses reasonably related to or incidental to such
specified uses, all (i) consistent with first class life sciences projects in the Torrey Pines area of San Diego, California (“First Class Life Sciences Projects”), and (ii) in compliance with, and
subject to, applicable laws and the terms of this Lease.
		
	8.     Security Deposit (Article 21):	  	$29,532.23.
		
	9.     Parking (Article 28):	  	Twenty (20) unreserved parking spaces, subject to the terms of Article 28 of this Lease.

  

  

					
		  	-2-	  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

			
	10.     Address of Tenant (Section 29.18):	  	 Synthorx Inc.
 11099 North Torrey Pines Road,
Suite 290
 San Diego, California 92037
 Attention: Legal
Department
 (Prior to Lease Commencement Date)
  

and
  

		  	 Synthorx Inc.
 11099 North Torrey Pines Road,
Suite 190
 San Diego, California 92037
 Attention: Legal
Department
 (After Lease Commencement Date)

		
	11.     Address of Landlord (Section 29.18):	  	See Section 29.18 of this Lease.
		
	12.     Broker (Section 29.24):	  	Hughes Marino, Inc.

  

					
		  	-3-	  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

 1. PREMISES, BUILDING, PROJECT, AND COMMON AREAS 

1.1 Premises, Building, Project and Common Areas. 

1.1.1 The Premises. Landlord hereby leases to Tenant and Tenant hereby leases from Landlord the premises set forth in
Section 2.2 of the Summary (the “Premises”). The outline of the Premises is set forth in Exhibit A attached hereto. The outline of the “Building” and
the “Project,” as those terms are defined in Section 1.1.2 below, are further depicted on the Site Plan attached hereto as Exhibit A-1. The parties hereto
agree that the lease of the Premises is upon and subject to the terms, covenants and conditions herein set forth, and Tenant covenants as a material part of the consideration for this Lease to keep and perform each and all of such terms, covenants
and conditions by it to be kept and performed and that this Lease is made upon the condition of such performance. The parties hereto hereby acknowledge that the purpose of Exhibit A is to show the
approximate location of the Premises only, and such Exhibit is not meant to constitute an agreement, representation or warranty as to the construction of the Premises, the precise area thereof or the specific location of the “Common
Areas,” as that term is defined in Section 1.1.3, below, or the elements thereof or of the accessways to the Premises or the “Project,” as that term is defined in Section 1.1.2,
below. Except as specifically set forth in this Lease and in the Tenant Work Letter, Landlord shall not be obligated to provide or pay for any improvement work or services related to the improvement of the Premises. Tenant also acknowledges that
neither Landlord nor any agent of Landlord has made any representation or warranty regarding the condition of the Premises, the Building or the Project or with respect to the suitability of any of the foregoing for the conduct of Tenant’s
business, except as specifically set forth in this Lease and the Tenant Work Letter. The taking of possession of the Premises by Tenant shall conclusively establish that the Premises and the Building were at such time in good and sanitary order,
condition and repair, subject to Section 1.1.4 and minor “punchlist” matters related to the Building brought to Landlord’s attention within ten (10) days after Tenant commences business operations from
the Premises. 
 1.1.2 The Building and The Project. The Premises constitutes a portion of the building set forth in
Section 2.1 of the Summary (the “Building”). The Building is part of an office/laboratory project currently known as “11099 North Torrey Pines Road.” The term “Project,” as used
in this Lease, shall mean (i) the Building and the Common Areas, (ii) the land (which is improved with landscaping, parking facilities and other improvements) upon which the Building and the Common Areas are located, and (iii) at
Landlord’s discretion, any additional real property, areas, land, buildings or other improvements added thereto outside of the Project. 

1.1.3 Common Areas. Tenant shall have the non-exclusive right to use in common with other
tenants in the Project, and subject to the rules and regulations referred to in Article 5 of this Lease, those portions of the Project which are provided, from time to time, for use in common by Landlord, Tenant and any other tenants of the
Project (such areas, together with such other portions of the Project designated by Landlord, in its discretion, are collectively referred to herein as the “Common Areas”). The Common Areas shall be maintained in a condition
consistent with First Class Life Sciences Projects, and the use thereof shall be subject to such reasonable rules, regulations and restrictions as Landlord may make from time to time. Any rules and regulations established by the Landlord for
use of the Common Areas shall not unreasonably restrict Tenant’s access to or use of the Premises for conduct of its business, nor diminish Tenant’s rights under this Lease. In the event of any conflict between such rules and regulations
and the terms of this Lease, the latter shall control. Landlord reserves the right to close temporarily, make alterations or additions to, or change the location of elements of the Project and the Common Areas, provided that, in connection
therewith, Landlord shall use commercially reasonable efforts to minimize any material interference with Tenant’s use of and access to the Premises. 

1.1.4 Condition of Building Systems. Notwithstanding anything set forth in Section 1.1.1, above, to the
contrary, Landlord shall cause the base Building roof, lighting, mechanical (including HVAC), electrical, fire suppression and plumbing systems located in the internal core of the Building and which serve the Premises (the “Warrantied
Items”) to be in good working condition and repair upon the Lease Commencement Date. The foregoing shall not be deemed to require Landlord to replace any of the Warrantied Items, as opposed to repair any Warrantied Items. Provided Tenant
notifies Landlord prior to the first (1st) anniversary of the Lease Commencement Date, Landlord shall, at Landlord’s sole cost and expense (which shall not be deemed an “Operating
Expense,” as that term is defined in Article 4), repair or replace any portion of the Warrantied Item which was not in good working 

  

					
		  		  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

 
condition on the Lease Commencement Date, provided that the need to repair or replace was not caused (A) by the misuse, misconduct, damage, destruction, omissions, and/or negligence of
Tenant, its subtenants and/or assignees, if any, or any company which is acquired, sold or merged with Tenant (collectively, “Tenant Damage”), or (B) by any modifications, Alterations or improvements constructed by or on behalf
of Tenant. Landlord’s obligation pursuant to the immediately preceding sentence shall not extend to the costs of normal and customary preventive maintenance relating to the Warrantied Item. To the extent repairs which Landlord is required to
make pursuant to this Section 1.1.4 are necessitated in part by Tenant Damage, then Tenant shall reimburse Landlord for an equitable proportion of the cost of such repair. If it is determined that the Warrantied Item
was not in good working condition and repair as of the Lease Commencement Date, Landlord shall not be liable to Tenant for any damages, but, as Tenant’s sole remedy, Landlord, at no cost to Tenant, shall promptly commence such work or take such
other action as may be necessary to place the same in good working condition and repair, and shall thereafter diligently pursue the same to completion. 

1.2 Rentable Square Feet of Building and Premises. The rentable square footage of the Building and the Premises are hereby deemed
to be as set forth in Sections 2.1 and 2.2 of the Summary, respectively, and shall not be subject to measurement or adjustment during the Lease Term. 

1.3 Outside Ready for Occupancy Date.    Notwithstanding anything contained herein to the contrary, if the
Premises are not Ready for Occupancy (or not deemed to be Ready for Occupancy) on or prior to March 1, 2019 (the “Outside Ready for Occupancy Date”, which date shall be extended on a day-for-day basis for each day Landlord is delayed in causing the Premises to be Ready for Occupancy as a result of any delays due to Force Majeure, as that term is defined in
Section 29.16 of this Lease, or Tenant Delay, as that term is defined in Section 5.2 of the Tenant Work Letter), then Tenant shall have the right to deliver a written notice to Landlord (a
“Termination Notice”) electing to terminate this Lease effective upon the date occurring five (5) business days following receipt by Landlord of the Termination Notice (the “Effective Termination Date”). The
Termination Notice must be delivered by Tenant to Landlord, if at all, not earlier than the Outside Ready for Occupancy Date nor later than five (5) business days after the Outside Ready for Occupancy Date. The effectiveness of any such
Termination Notice delivered by Tenant to Landlord shall be governed by the terms of this Section 1.3. If Tenant delivers a Termination Notice to Landlord, then Landlord shall have the right to suspend the occurrence of the
Effective Termination Date for a period ending thirty (30) days after the Outside Ready for Occupancy Date by delivering written notice to Tenant, prior to the Effective Termination Date, that, in Landlord’s reasonable, good faith
judgment, the Premises will be Ready for Occupancy (or deemed to be Ready for Occupancy) within thirty (30) days after the Outside Ready for Occupancy Date (the “Termination Extension Notice”). If the Premises are Ready for
Occupancy (or deemed to be Ready for Occupancy) within such thirty (30) day suspension period, then the Termination Notice shall be of no force or effect, but if the Premises are not Ready for Occupancy (or not deemed to be Ready for Occupancy)
within such thirty (30) day suspension period, then this Lease shall terminate and have no further force or effect upon the expiration of such thirty (30) day suspension period and Landlord shall refund to Tenant any prepaid Base Rent and
the Security Deposit paid by Tenant to Landlord. The rights and remedies set forth in this Section 1.3 shall be Tenant’s sole rights and remedies available to it in connection with Landlord’s failure to cause the
Premises to be Ready for Occupancy (or deemed to be Ready for Occupancy) by any particular date. 
 2. LEASE TERM; OPTION TERM 

2.1 Lease Term. The terms and provisions of this Lease shall be effective as of the date of this Lease. The term of this Lease
(the “Lease Term”) shall be as set forth in Section 3.1 of the Summary, shall commence on the date set forth in Section 3.2 of the Summary (the “Lease Commencement Date”), and shall terminate
on the date set forth in Section 3.3 of the Summary (the “Lease Expiration Date”) unless this Lease is sooner terminated as hereinafter provided. For purposes of this Lease, the term “Lease Year” shall
mean each consecutive twelve (12) month period during the Lease Term; provided, however, that the first (1st) Lease Year shall commence on the Lease Commencement Date and end on the last day of the month in which the first (1st) anniversary of
the Lease Commencement Date occurs (or if the Lease Commencement Date is the first (1st) day of a calendar month, then the first (1st) Lease Year shall end on the day preceding the first (1st) anniversary of the Lease Commencement Date), and the
second and each succeeding Lease Year shall commence on the first (1st) day of the next calendar month; provided further that the last Lease Year shall end on the Lease Expiration Date (or, if applicable, the last day of the Option Term). At any
time during the Lease Term, Landlord may deliver to Tenant a notice in the form as set forth in Exhibit C, attached hereto, as a confirmation only of the information set forth therein, which Tenant shall execute

  

					
		  	-5-	  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

 
and return to Landlord within ten (10) business days of receipt thereof; provided, however, that if such notice is not factually correct, then Tenant shall make such changes as are necessary
to make such notice factually correct and shall thereafter return such notice to Landlord within said ten (10) business day period. Tenant’s failure to execute and return such notice to Landlord within such time shall be conclusive upon
Tenant that the information set forth in such notice is as specified therein. 
 2.2 Option Term. 

2.2.1 Option Right. Landlord hereby grants the Tenant originally named in this Lease (the “Original Tenant”),
and any “Permitted Transferee Assignee,” as that term is defined in Section 14.8, below, one (1) option to extend the Lease Term for a period of one (1) year (the “Option Term”). Such
option to extend shall be exercisable only by written notice delivered by Tenant to Landlord not less than six (6) months prior to the expiration of the initial Lease Term, stating that Tenant is thereby irrevocably exercising its option to
lease the Premises during the Option Term. Upon the proper exercise of the option to extend, and provided that, at Landlord’s option, as of the date of delivery of such notice, Tenant is not in default under this Lease and has not previously
been in default (beyond the expiration of any applicable notice and cure period expressly set forth in this Lease) under this Lease more than once during the immediately preceding twelve (12) month period, and as of the end of the Lease Term,
Tenant is not in default under this Lease (beyond the expiration of any applicable notice and cure period expressly set forth in this Lease), the Lease Term shall be extended for a period of one (1) year. The rights contained in this
Section 2.2 shall be personal to Original Tenant and any Permitted Transferee Assignee (and not any other assignee, sublessee or “Transferee,” as that term is defined in Section 14.1,
below, of Tenant’s interest in this Lease). In the event that Tenant fails to timely and appropriately exercise its option to extend the Lease Term in accordance with the terms of this Section 2.2, then such option
shall automatically terminate and shall be of no further force or effect. 
 2.2.2 Option Rent. The Base Rent payable by Tenant
during the Option Term (the “Option Rent”) for all of the Premises shall be as set forth in Section 4 of the Summary. 

3. BASE RENT 
 3.1 Base Rent.
Tenant shall pay, without prior notice or demand, to Landlord or Landlord’s agent at the management office of the Project, or, at Landlord’s option, at such other place as Landlord may from time to time designate in writing, by a check for
currency which, at the time of payment, is legal tender for private or public debts in the United States of America, base rent (“Base Rent”) as set forth in Section 4 of the Summary, payable in equal monthly installments
as set forth in Section 4 of the Summary in advance on or before the first day of each and every calendar month during the Lease Term, without any setoff or deduction whatsoever. The Base Rent for the first full month of the Lease Term
following the expiration of the “Rent Abatement Period,” as that term is defined in Section 3.2, below, shall be paid at the time of Tenant’s execution of this Lease. If any Rent payment date (including the
Lease Commencement Date) falls on a day of the month other than the first day of such month or if any payment of Rent is for a period which is shorter than one month, the Rent for any fractional month shall accrue on a daily basis for the period
from the date such payment is due to the end of such calendar month or to the end of the Lease Term at a rate per day which is equal to 1/365 of the applicable annual Rent. All other payments or adjustments required to be made under the terms of
this Lease that require proration on a time basis shall be prorated on the same basis. 
 3.2 Abated Base Rent. Provided that
Tenant is not then in default of this Lease (beyond the expiration of any applicable notice and cure period expressly set forth in this Lease), then during the period commencing on the first day of the first (1st) full calendar month of the Lease Term and continuing through and including the last day of the fourth (4th) full calendar month of the Lease
Term (the “Rent Abatement Period”), Tenant shall not be obligated to pay any Base Rent otherwise attributable to the Premises during such Rent Abatement Period (the “Rent Abatement”). Landlord and Tenant acknowledge
that the aggregate amount of the Rent Abatement equals $104,956.00 (i.e., $26,239.00 per month). Tenant acknowledges and agrees that the foregoing Rent Abatement has been granted to Tenant as additional consideration for entering into this Lease,
and for agreeing to pay the rental and performing the terms and conditions otherwise required under this Lease. If Tenant shall be in default under this Lease, and shall fail to cure such default within the notice and cure period, if any, permitted
for cure pursuant to terms and conditions of the Lease, or if this Lease is terminated for any reason other than Landlord’s breach of this Lease, then the dollar amount of the unapplied portion of the Rent Abatement as of the date of such
default or termination, 

  

					
		  	-6-	  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

 
as the case may be, shall be converted to a credit to be applied to the Base Rent applicable at the end of the Lease Term and Tenant shall immediately be obligated to begin paying Base Rent for
the Premises in full. 
 4. ADDITIONAL RENT 

4.1 General Terms. 

4.1.1 Direct Expenses; Additional Rent. In addition to paying the Base Rent specified in Article 3 of this Lease, Tenant
shall pay Tenant’s Share of the annual Direct Expenses. Such payments by Tenant, together with any and all other amounts payable by Tenant to Landlord pursuant to the terms of this Lease, are hereinafter collectively referred to as the
“Additional Rent”, and the Base Rent and the Additional Rent are herein collectively referred to as “Rent.” All amounts due under this Article 4 as Additional Rent shall be payable for the same periods and in
the same manner as the Base Rent. Without limitation on other obligations of Tenant which survive the expiration of the Lease Term, the obligations of Tenant to pay the Additional Rent provided for in this Article 4 shall survive the
expiration of the Lease Term. 
 4.1.2 Triple Net Lease. Landlord and Tenant acknowledge that, except as otherwise provided to
the contrary in this Lease, it is their intent and agreement that this Lease be a “TRIPLE NET” lease and that as such, the provisions contained in this Lease are intended to pass on to Tenant or reimburse Landlord for the
costs and expenses reasonably associated with this Lease, the Building and the Project, and Tenant’s operation therefrom, subject to Section 4.2, below. To the extent such costs and expenses payable by Tenant cannot be charged directly to,
and paid by, Tenant, such costs and expenses shall be paid by Landlord but reimbursed by Tenant as Additional Rent. 
 4.2 Definitions
of Key Terms Relating to Additional Rent. As used in this Article 4, the following terms shall have the meanings hereinafter set forth: 

4.2.1 Intentionally Deleted.  

4.2.2 “Direct Expenses” shall mean “Operating Expenses” and “Tax Expenses.” 

4.2.3 “Expense Year” shall mean each calendar year in which any portion of the Lease Term falls, through and including the
calendar year in which the Lease Term expires, provided that Landlord, upon written notice to Tenant, may change the Expense Year from time to time to any other twelve (12) consecutive month period, and, in the event of any such change,
Tenant’s Share of Direct Expenses shall be equitably adjusted for any Expense Year involved in any such change. 
 4.2.4
“Operating Expenses” shall mean all expenses, costs and amounts of every kind and nature which Landlord pays or accrues during any Expense Year because of or in connection with the ownership, management, maintenance, security,
repair, replacement, restoration or operation of the Project, or any portion thereof, as determined in accordance with sound real estate management and accounting practices, consistently applied. Without limiting the generality of the foregoing,
Operating Expenses shall specifically include any and all of the following: (i) the cost of supplying all utilities, the cost of operating, repairing, maintaining, and renovating the utility, telephone, mechanical, sanitary, storm drainage, and
elevator systems, and the cost of maintenance and service contracts in connection therewith; (ii) the cost of licenses, certificates, permits and inspections and the cost of contesting any governmental enactments which may affect Operating
Expenses, and the costs incurred in connection with a governmentally mandated transportation system management program or similar program; (iii) the cost of all insurance carried by Landlord in connection with the Project and Premises as
reasonably determined by Landlord; (iv) the cost of landscaping, relamping, and all supplies, tools, equipment and materials used in the operation, repair and maintenance of the Project, or any portion thereof; (v) the cost of parking area
operation, repair, restoration, and maintenance; (vi) fees and other costs, including management and/or incentive fees, consulting fees, legal fees and accounting fees, of all contractors and consultants in connection with the management,
operation, maintenance and repair of the Project; (vii) payments under any equipment rental agreements and the fair rental value of any management office space; (viii) subject to item (f), below, wages, salaries and other compensation and
benefits, including taxes levied thereon, of all persons engaged in the operation, maintenance and security of the Project; (ix) costs under any instrument pertaining to the sharing of costs by the Project; (x) operation, repair,
maintenance and 

  

					
		  	-7-	  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

 
replacement of all systems and equipment and components thereof of the Project; (xi) the cost of janitorial, alarm, security and other services, replacement of wall and floor coverings,
ceiling tiles and fixtures in common areas, maintenance and replacement of curbs and walkways, repair to roofs and re-roofing; (xii) amortization (including interest on the unamortized cost) of the cost
of acquiring or the rental expense of personal property used in the maintenance, operation and repair of the Project, or any portion thereof (which shall be amortized over its useful life as Landlord shall reasonably determine in accordance with
sound real estate management and accounting practices, consistently applied); (xiii) the cost of capital improvements or other costs incurred in connection with the Project (A) which are intended to effect economies in the operation or
maintenance of the Project, or any portion thereof, or to reduce current or future Operating Expenses (provided that the amortized amount included in any Expense Year shall not exceed the reasonably anticipated cost savings), or to enhance the
safety or security of the Project or its occupants, (B) that are required to comply with present or anticipated conservation programs required under applicable laws, (C) which are replacements or modifications of nonstructural items
located in the Common Areas required to keep the Common Areas in good order or condition, (D) that are required under any governmental law or regulation, except for capital expenditures to remedy a condition existing prior to the Lease
Commencement Date which an applicable governmental authority, if it had knowledge of such condition prior to the Lease Commencement Date, would have then required to be remedied pursuant to then-current governmental laws or regulations in their form
existing as of the Lease Commencement Date and pursuant to the then-current interpretation of such governmental laws or regulations by the applicable governmental authority as of the Lease Commencement Date, or (E) which are reasonably
necessary repairs, replacements or modifications to the “Building Systems” (as defined in Section 7.1, below); provided, however, that any capital expenditure shall be amortized (including commercially reasonable
interest on the amortized cost) over the useful life of such capital item as Landlord shall reasonably determine in accordance with sound real estate management and accounting practices, consistently applied; and (xiv) costs, fees, charges or
assessments imposed by, or resulting from any mandate imposed on Landlord by, any federal, state or local government for fire and police protection, trash removal, community services, or other services which do not constitute “Tax
Expenses” as that term is defined in Section 4.2.5, below, and (xvmef) payments under any easement, license, operating agreement, declaration, restrictive covenant, or instrument pertaining to the sharing of costs
by the Building, including, without limitation, any covenants, conditions and restrictions affecting the property, and reciprocal easement agreements affecting the property, any parking licenses, and any agreements with transit agencies affecting
the Property (collectively, “Underlying Documents”). Notwithstanding the foregoing, for purposes of this Lease, Operating Expenses shall not, however, include: 

(a) costs, including legal fees, space planners’ fees, advertising and promotional expenses (except as otherwise set forth
above), and brokerage fees incurred in connection with the original construction or development, or original or future leasing of the Project, and costs, including permit, license and inspection costs, incurred with respect to the installation of
tenant improvements made for new tenants initially occupying space in the Project after the Lease Commencement Date or incurred in renovating or otherwise improving, decorating, painting or redecorating vacant space for tenants or other occupants of
the Project (excluding, however, such costs relating to any Common Areas), and any costs or expenses incurred in connection with the relocation of any tenants, and costs for the repair or replacement of the Base Building (or any component thereof)
made necessary as a result of latent defects in the original design, workmanship or materials; 
 (b) except as set forth in
items (xii), (xiii), and (xiv) above, depreciation, interest and principal payments on mortgages and other debt costs, if any, penalties and interest, costs of capital repairs, replacements and alterations, and costs of capital improvements and
equipment; 
 (c) costs for which the Landlord is reimbursed by any tenant or occupant of the Project or by insurance by its
carrier (or would have been reimbursed if Landlord had carried the insurance Landlord is required to carry pursuant to this Lease) or any tenant’s carrier or by anyone else, and utility costs for which any tenant directly contracts with the
local public service company; 
 (d) any bad debt loss, rent loss, or reserves for bad debts or rent loss; 

(e) costs associated with the operation of the business of the partnership or entity which constitutes the Landlord, as the
same are distinguished from the costs of operation of the Project (which 

  

					
		  	-8-	  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

 
shall specifically include, but not be limited to, accounting costs associated with the operation of the Project). Costs associated with the operation of the business of the partnership or entity
which constitutes the Landlord include costs of partnership accounting and legal matters, costs of defending any lawsuits with any mortgagee (except as the actions of the Tenant may be in issue), costs of selling, syndicating, financing, mortgaging
or hypothecating any of the Landlord’s interest in the Project, and costs incurred in connection with any disputes between Landlord and its employees, between Landlord and Project management, or between Landlord and other tenants or occupants;

 (f) the wages and benefits of any employee who does not devote substantially all of his or her employed time to the
Project unless such wages and benefits are prorated to reflect time spent on operating and managing the Project vis-a-vis time spent on matters unrelated to operating
and managing the Project; provided, that in no event shall Operating Expenses for purposes of this Lease include wages and/or benefits attributable to personnel above the level of Project manager; 

(g) amount paid as ground rental for the Project by the Landlord; 

(h) except for a Project management fee to the extent allowed pursuant to item (q) below, overhead and profit increment
paid to the Landlord or to subsidiaries or affiliates of the Landlord for services in the Project to the extent the same exceeds the costs of such services rendered by qualified, first-class unaffiliated third parties on a competitive basis; 

(i) any compensation paid to clerks, attendants or other persons in commercial concessions operated by the Landlord, provided
that any compensation paid to any concierge at the Project shall be includable as an Operating Expense; 
 (j) rentals and
other related expenses incurred in leasing air conditioning systems, elevators or other equipment which if purchased the cost of which would be excluded from Operating Expenses as a capital cost, except equipment not affixed to the Project which is
used in providing engineering, janitorial or similar services and, further excepting from this exclusion such equipment rented or leased to remedy or ameliorate an emergency condition in the Project; 

(k) all items and services for which Tenant or any other tenant in the Project reimburses Landlord or which Landlord provides
selectively to one or more tenants (other than Tenant) without reimbursement; 
 (l) any costs expressly excluded from
Operating Expenses elsewhere in this Lease; 
 (m) rent for any office space occupied by Project management personnel to the
extent the size or rental rate of such office space exceeds the size or fair market rental value of office space occupied by management personnel of the comparable buildings in the vicinity of the Building, with adjustment where appropriate for the
size of the applicable project; 
 (n) costs arising from the gross negligence or willful misconduct of Landlord or any
Landlord Party (as that term is defined in Section 10.1 below), in connection with this Lease; 

(o) costs incurred to comply with laws relating to the removal of hazardous material (as defined under applicable law) which
was in existence in the Building or on the Project prior to the Lease Commencement Date, and was of such a nature that a federal, State or municipal governmental authority, if it had then had knowledge of the presence of such hazardous material, in
the state, and under the conditions that it then existed in the Building or on the Project, would have then required the removal of such hazardous material or other remedial or containment action with respect thereto; and costs incurred to remove,
remedy, contain, or treat hazardous material, which hazardous material is brought into the Building or onto the Project after the date hereof by Landlord or any other tenant of the Project and is of such a nature, at that time, that a federal, State
or municipal governmental authority, if it had then had knowledge of the presence of such hazardous material, in the state, and under the conditions, that it then exists in the Building or on the Project,

  

					
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[Synthorx Inc.]

 
would have then required the removal of such hazardous material or other remedial or containment action with respect thereto; 

(p) costs of items considered capital repairs, replacements, improvements and equipment under sound real estate management and
accounting principles consistently applied, except as expressly included in Operating Expenses pursuant to the definition above, including, without limitation, as otherwise set forth in item (xiii) of
Section 4.2.4 above; and 
 (q) fees payable by Landlord for management of the Project in excess of
three percent (3%) (the “Management Fee Cap”) of Landlord’s gross rental revenues, adjusted and grossed up to reflect a one hundred percent (100%) occupancy of the Project with all tenants paying full rent, as contrasted with
free rent, half-rent and the like, including base rent, pass-throughs, and parking fees from the Project for any calendar year or portion thereof 

If Landlord is not furnishing any particular work or service (the cost of which, if performed by Landlord, would be included in Operating
Expenses) to a tenant who has undertaken to perform such work or service in lieu of the performance thereof by Landlord, Operating Expenses shall be deemed to be increased by an amount equal to the additional Operating Expenses which would
reasonably have been incurred during such period by Landlord if it had at its own expense furnished such work or service to such tenant. If the Project is not at least one hundred percent (100%) occupied during all or a portion of any Expense Year,
Landlord may elect to make an appropriate adjustment to the components of Operating Expenses for such year to determine the amount of Operating Expenses that would have been incurred had the Project been one hundred percent (100%) occupied; and the
amount so determined shall be deemed to have been the amount of Operating Expenses for such year. Any cost or expense of the nature described above shall be included in Operating Expenses for any Expense Year no more than once in such year,
notwithstanding that such cost or expense may fall under more than one of the categories listed above. Landlord shall not (i) make a profit by charging items to Operating Expenses that are otherwise also charged separately to others and
(ii) subject to Landlord’s right to adjust the components of Operating Expenses described above in this paragraph, collect Operating Expenses from Tenant and all other tenants in the Building in an amount in excess of what Landlord incurs
for the items included in Operating Expenses. 
 4.2.5 Taxes. 

4.2.5.1 “Tax Expenses” shall mean all federal, state, county, or local governmental or municipal taxes, fees, charges or
other impositions of every kind and nature, whether general, special, ordinary or extraordinary (including, without limitation, real estate taxes, general and special assessments, transit taxes, leasehold taxes or taxes based upon the receipt of
rent, including gross receipts or sales taxes applicable to the receipt of rent, unless required to be paid by Tenant, personal property taxes imposed upon the fixtures, machinery, equipment, apparatus, systems and equipment, appurtenances,
furniture and other personal property used in connection with the Project, or any portion thereof), which shall be paid or accrued during any Expense Year (without regard to any different fiscal year used by such governmental or municipal authority)
because of or in connection with the ownership, leasing and operation of the Project, or any portion thereof. 
 4.2.5.2 Tax Expenses shall
include, without limitation: (i) Any tax on the rent, right to rent or other income from the Project, or any portion thereof, or as against the business of leasing the Project, or any portion thereof; (ii) Any assessment, tax, fee, levy or
charge in addition to, or in substitution, partially or totally, of any assessment, tax, fee, levy or charge previously included within the definition of real property tax; (iii) Any assessment, tax, fee, levy, or charge allocable to or
measured by the area of the Premises or the Rent payable hereunder, including, without limitation, any business or gross income tax or excise tax with respect to the receipt of such rent, or upon or with respect to the possession, leasing,
operating, management, maintenance, alteration, repair, use or occupancy by Tenant of the Premises, or any portion thereof; and (iv) Any assessment, tax, fee, levy or charge, upon this transaction or any document to which Tenant is a party,
creating or transferring an interest or an estate in the Premises or the improvements thereon. 
 4.2.5.3 Any costs and expenses (including,
without limitation, reasonable attorneys’ and consultants’ fees) incurred in attempting to protest, reduce or minimize Tax Expenses shall be included in Tax 

  

					
		  	-10-	  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

 
Expenses in the Expense Year such expenses are incurred. Tax refunds shall be credited against Tax Expenses and refunded to Tenant regardless of when received, based on the Expense Year to which
the refund is applicable, provided that in no event shall the amount to be refunded to Tenant for any such Expense Year exceed the total amount paid by Tenant as Additional Rent under this Article 4 for such Expense Year. If Tax Expenses for any
period during the Lease Term or any extension thereof are increased after payment thereof for any reason, including, without limitation, error or reassessment by applicable governmental or municipal authorities, Tenant shall pay Landlord, within
thirty (30) days of Landlord’s request, together with supporting documentation of such change, Tenant’s Share of any such increased Tax Expenses. Notwithstanding anything to the contrary contained in this
Section 4.2.5, there shall be excluded from Tax Expenses (i) all excess profits taxes, franchise taxes, gift taxes, capital stock taxes, inheritance and succession taxes, estate taxes, federal and state income taxes,
and other taxes to the extent applicable to Landlord’s net income (as opposed to rents, receipts or income attributable to operations at the Project), (ii) any items included as Operating Expenses, (iii) any items paid by Tenant under
Section 4.5 of this Lease, and (iv) any fees, penalties or interest incurred due to Landlord’s failure to pay any Tax Expenses as and when due. 

4.2.6 “Tenant’s Share” shall mean the percentage set forth in Section 6 of the Summary. 

4.3 Allocation of Direct Expenses. The parties acknowledge that the Building is a part of a multi-building project and that the
costs and expenses incurred in connection with the Project (i.e., the Direct Expenses) should be shared between the Building and the other buildings in the Project. Accordingly, as set forth in Section 4.2 above, Direct
Expenses (which consist of Operating Expenses and Tax Expenses) are determined annually for the Project as a whole, and a portion of the Direct Expenses, which portion shall be determined by Landlord on an equitable basis, shall be allocated to the
Building (as opposed to other buildings in the Project). Such portion of Direct Expenses allocated to the Building shall include all Direct Expenses attributable solely to the Building and an equitable portion of the Direct Expenses attributable to
the Project as a whole, and shall not include Direct Expenses attributable solely to other buildings in the Project. 
 4.4 Calculation
and Payment of Additional Rent. Tenant shall pay to Landlord, in the manner set forth in Section 4.4.1, below, and as Additional Rent, Tenant’s Share of Direct Expenses for each Expense Year. Notwithstanding
anything to the contrary contained in this Article 4, the aggregate “Controllable Expenses,” as that term is defined below, included in Direct Expenses in any Expense Year after the first (1st) Expense Year shall never be increased to an amount in excess of the amount that such Controllable Expenses would currently be had they increased, from the initial amount for such Controllable
Expenses set forth in the first (1st) Expense Year, at a cumulative rate of five percent (5%) per Expense Year. For purposes of this Section 4.4,
“Controllable Expenses” shall mean all Direct Expenses except: (i) Tax Expenses and any and all assessments, including assessment districts and government-mandated charges with respect to the Building or Project, or any part
thereof; (ii) insurance carried by Landlord; and (iii) costs of utilities, including, without limitation, electricity, water, HVAC and sewer charges, utility surcharges and assessments, and refuse removal. The terms Controllable Expenses
shall also exclude the costs of capital alterations, capital additions, capital improvements, capital repairs and capital replacements to the extent included in Operating Expenses pursuant to the definition in
Section 4.2.4, above; and costs to repair caused by any casualty, vandalism or events of Force Majeure. 
 4.4.1
Statement of Actual Direct Expenses and Payment by Tenant. Landlord shall use commercially reasonable efforts to give to Tenant within one hundred fifty (150) days following the end of each Expense Year, a statement (the
“Statement”) which shall state the Direct Expenses incurred or accrued for such preceding Expense Year, and which shall indicate the amount of Tenant’s Share of Direct Expenses. Upon receipt of the Statement for each Expense
Year commencing or ending during the Lease Term, Tenant shall pay, with its next installment of Base Rent due, the full amount of Tenant’s Share of Direct Expenses for such Expense Year, less the amounts, if any, paid during such Expense Year
as “Estimated Direct Expenses,” as that term is defined in Section 4.4.2, below, and if Tenant paid more as Estimated Direct Expenses than the actual Tenant’s Share of Direct Expenses, Tenant shall receive a
credit in the amount of Tenant’s overpayment against Rent next due under this Lease. The failure of Landlord to timely furnish the Statement for any Expense Year shall not prejudice Landlord or Tenant from enforcing its rights under this
Article 4. Even though the Lease Term has expired and Tenant has vacated the Premises, when the final determination is made of Tenant’s Share of Direct Expenses for the Expense Year in which this Lease terminates, if Tenant’s Share
of Direct Expenses is greater than the amount of Estimated Direct Expenses previously paid by Tenant to Landlord, Tenant shall, within thirty (30) days after receipt of the Statement, pay such 

  

					
		  	-11-	  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

 
shortfall to Landlord, and if Tenant paid more as Estimated Direct Expenses than the actual Tenant’s Share of Direct Expenses, Landlord shall, within thirty (30) days after delivery of
the applicable Statement to Tenant, deliver a check payable to Tenant in the amount of the overpayment. The provisions of this Section 4.4.1 shall survive the expiration or earlier termination of the Lease Term, provided
that, other than Tax Expenses and costs incurred for utilities, Tenant shall not be responsible for Tenant’s Share of any Operating Expenses which are first billed to Tenant more than eighteen (18) months after the end of the Expense Year
to which such Operating Expenses relate. 
 4.4.2 Statement of Estimated Direct Expenses. In addition, Landlord shall use
commercially reasonable efforts to give Tenant, on or prior to February 1 of each Expense Year during the Lease Term, a reasonably detailed yearly expense estimate statement (the “Estimate Statement”) which shall set forth
Landlord’s reasonable estimate (the “Estimate”) of what the total amount of Direct Expenses for the then-current Expense Year shall be and the estimated Tenant’s Share of Direct Expenses (the “Estimated Direct
Expenses”). The failure of Landlord to timely furnish the Estimate Statement for any Expense Year shall not preclude Landlord from enforcing its rights to collect any Estimated Direct Expenses under this Article 4, nor shall Landlord
be prohibited from revising any Estimate Statement or Estimated Direct Expenses theretofore delivered to the extent necessary. Thereafter, Tenant shall pay, with its next installment of Base Rent due, a fraction of the Estimated Direct Expenses for
the then-current Expense Year (reduced by any amounts paid pursuant to the last sentence of this Section 4.4.2). Such fraction shall have as its numerator the number of months which have elapsed in such current Expense
Year, including the month of such payment, and twelve (12) as its denominator. Until a new Estimate Statement is furnished (which Landlord shall have the right to deliver to Tenant at any time), Tenant shall pay monthly, with the monthly Base
Rent installments, an amount equal to one-twelfth (1/12) of the total Estimated Direct Expenses set forth in the previous Estimate Statement delivered by Landlord to Tenant. 

4.5 Taxes and Other Charges for Which Tenant Is Directly Responsible. Tenant shall be liable for and shall pay before
delinquency, taxes levied against Tenant’s equipment, furniture, fixtures and any other personal property located in or about the Premises. If any such taxes on Tenant’s equipment, furniture, fixtures and any other personal property are
levied against Landlord or Landlord’s property or if the assessed value of Landlord’s property is increased by the inclusion therein of a value placed upon such equipment, furniture, fixtures or any other personal property and if Landlord
pays the taxes based upon such increased assessment, which Landlord shall have the right to do regardless of the validity thereof but only under proper protest if requested by Tenant, Tenant shall, within thirty (30) days of Landlord’s
demand, repay to Landlord the taxes so levied against Landlord or the proportion of such taxes resulting from such increase in the assessment, as the case may be. 

4.6 Landlord’s Books and Records. Notwithstanding anything to the contrary contained in this Lease, if, within one hundred
eighty (180) days after receipt of a Statement by Tenant, Tenant (i) reasonably disputes any amounts set forth in any Statement described above in this Article 4, and (ii) no Event of Default has occurred and
is continuing, then Tenant shall have the right to cause Landlord’s books and records to be audited by a firm of certified public accountants reasonably approved by Landlord, at no cost or expense to Landlord (except as provided below), which
has prior experience in the review of financial statements and which shall not be retained by Tenant on a contingency fee basis; provided, however, Tenant shall not have the right to perform any such audit more than one (1) time for any Expense
Year during the Lease Term. Any audit conducted by or on behalf of Tenant shall be completed in a diligent manner and timely manner (but in any event within two (2) months after Tenant initially disputes the applicable Statement) and shall be
performed at Landlord’s office during Landlord’s normal business hours and in a manner so as to minimize interference with Landlord’s business operations. Landlord shall have no obligation and Tenant shall have no right to make
photocopies of any of Landlord’s ledgers, invoices or other items. Tenant agrees to keep, and to cause Tenant’s accountant and its employees to keep, all information revealed by any audit of Landlord’s books and records strictly
confidential and not to disclose any such information or permit any such information to be disclosed to anyone other than Landlord, unless compelled to do so by a court of law or any Applicable Law, statute, code, rule or regulation, and Tenant and
its accountant and their employees shall sign a confidentiality agreement reflecting such confidentiality. Tenant’s audit shall be limited to an on-site review of Landlord’s general ledger of
accounts and supporting documentation. If after such audit, Landlord disputes the results of such audit, at Landlord’s request, a certified public accounting firm selected by Landlord, and reasonably approved by Tenant, shall, at
Landlord’s cost, conduct an audit of the relevant Direct Expenses. The amounts payable under this Section 4.6 by Landlord to Tenant or by Tenant to Landlord, as the case may be, will be appropriately adjusted on the
basis of such audit. If such audit discloses an overstatement of Direct Expenses in excess of five percent (5%) 

  

					
		  	-12-	  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

 
for such Expense Year, Landlord shall reimburse Tenant for the reasonable cost of the first audit; otherwise the cost of such audit shall be borne by Tenant. Tenant agrees that this
Section 4.6 shall be the sole method to be used by Tenant to dispute the amount of any Direct Expenses payable by Tenant pursuant to the terms of this Lease, and Tenant hereby waives any other rights at law or in equity
relating thereto. The provisions of this Section 4.6 shall survive the expiration or earlier termination of the Lease Term. 

5. USE OF PREMISES 
 5.1 Permitted
Use. Tenant shall use the Premises solely for the Permitted Use set forth in Section 7 of the Summary and Tenant shall not use or permit the Premises or the Project to be used for any other purpose or purposes
whatsoever without the prior written consent of Landlord, which may be withheld in Landlord’s sole discretion. 
 5.2 Prohibited
Uses. Tenant further covenants and agrees that Tenant shall not use, or suffer or permit any person or persons to use, the Premises or any part thereof for any use or purpose in violation of the laws of the United States of America, the
State of California, or the ordinances, regulations or requirements of the local municipal or county governing body or other lawful authorities having jurisdiction over the Project) including, without limitation, any such laws, ordinances,
regulations or requirements relating to hazardous materials or substances, as those terms are defined by applicable laws now or hereafter in effect, or any Underlying Documents. Landlord shall have the right to impose reasonable and customary rule
and regulations regarding the use of the Project, as reasonably deemed necessary by Landlord with respect to the orderly operation of the Project, and Tenant shall comply with such reasonable rules and regulations provided to Tenant in writing or
posted to a conspicuous place in the Building; provided that in the event of a conflict between such rules and regulations and the terms of this Lease, the latter shall control. Tenant shall not do or permit anything to be done in or about the
Premises which will in any way damage the reputation of the Project or obstruct or interfere with the rights of other tenants or occupants of the Building, or injure or annoy them or use or allow the Premises to be used for any improper, unlawful or
objectionable purpose, nor shall Tenant cause, maintain or permit any nuisance in, on or about the Premises. Tenant shall comply with, and Tenant’s rights and obligations under the Lease and Tenant’s use of the Premises shall be subject
and subordinate to, all recorded easements, covenants, conditions, and restrictions now or hereafter affecting the Project, provided that, following the date of this Lease, Landlord shall not voluntarily enter into easements, covenants, conditions,
and restrictions that would unreasonably interfere with Tenant’s access to the Premises or use of the Premises for the Permitted Use. 

5.3 Hazardous Materials. 

5.3.1 Tenant’s Obligations. 

5.3.1.1 Prohibitions. As a material inducement to Landlord to enter into this Lease with Tenant, Tenant has fully and accurately
completed Landlord’s Pre-Leasing Environmental Exposure Questionnaire (the “Environmental Questionnaire”), which is attached as Exhibit E; provided, however, that Landlord
hereby acknowledges that the Hazardous Materials Chemical Inventory dated February 28, 2018 prepared for Tenant by ACT Environmental Services may be considered as the initial Environmental Questionnaire completed by Tenant. Tenant agrees that
except for those chemicals or materials, and their respective quantities, specifically listed on the Environmental Questionnaire (as updated from time to time), neither Tenant nor Tenant’s employees, contractors and subcontractors of any tier,
entities with a contractual relationship with Tenant (other than Landlord), or any entity acting as an agent or sub-agent of Tenant (collectively, “Tenant’s Agents”) will produce, use,
store or generate any “Hazardous Materials,” as that term is defined below, on, under or about the Premises, nor cause or permit any Hazardous Material to be brought upon, placed, stored, manufactured, generated, blended, handled,
recycled, used or “Released,” as that term is defined below, on, in, under or about the Premises. If any information provided to Landlord by Tenant on the Environmental Questionnaire, or otherwise relating to information concerning
Hazardous Materials is intentionally false, incomplete, or misleading in any material respect, the same shall be deemed an Event of Default by Tenant. Tenant shall deliver to Landlord an updated Environmental Questionnaire at least once a year
following a request by Landlord, and Tenant may update the Environmental Questionnaire (subject to Landlord’s reasonable approval) when Tenant anticipates a change in the types and amounts of Hazardous Materials Tenant will use in the Premises.
Landlord’s prior written consent shall be required to any Hazardous Materials use for the Premises not described on the Environmental Questionnaire as updated from time to time by Tenant, such consent to be withheld

  

					
		  	-13-	  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

 
only in Landlord’s commercially reasonable discretion. Tenant shall not install or permit any underground storage tank on the Premises. For purposes of this Lease, “Hazardous
Materials” means all flammable explosives, petroleum and petroleum products, waste oil, radon, radioactive materials, toxic pollutants, asbestos, polychlorinated biphenyls (“PCBs”), medical waste, chemicals known to cause
cancer or reproductive toxicity, pollutants, contaminants, hazardous wastes, toxic substances or related materials, including without limitation any chemical, element, compound, mixture, solution, substance, object, waste or any combination thereof,
which is or may be hazardous to human health, safety or to the environment due to its radioactivity, ignitability, corrosiveness, reactivity, explosiveness, toxicity, carcinogenicity, infectiousness or other harmful or potentially harmful properties
or effects, or defined as, regulated as or included in, the definition of “hazardous substances,” “hazardous wastes,” “hazardous materials,” or “toxic substances” under any Environmental Laws, except for de
minimis quantities of typical cleaning and office supplies, all of which shall be stored, used and disposed of in accordance with applicable laws. The term “Hazardous Materials” for purposes of this Lease shall also include any mold,
fungus or spores, whether or not the same is defined, listed, or otherwise classified as a “hazardous material” under any Environmental Laws, if such mold, fungus or spores may pose a risk to human health or the environment. For purposes
of this Lease, “Release” or “Released” or “Releases” shall mean any release, deposit, discharge, emission, leaking, spilling, seeping, migrating, injecting, pumping, pouring, emptying, escaping,
dumping, disposing, or other movement of Hazardous Materials into the environment. For the avoidance of doubt and notwithstanding anything to the contrary in this Lease, nothing in this Article 5 shall be construed to require any action by
Tenant that is inconsistent with the allocation of responsibility between Landlord and Tenant for the making of repairs or Alterations as provided in Articles 7 and/or 8. 

5.3.1.2 Notices to Landlord. Tenant shall notify Landlord in writing as soon as possible but in no event later than five
(5) days after (i) Tenant receives notice of or has knowledge of the occurrence of any actual, alleged or threatened Release of any Hazardous Material in, on, under, from, about or in the vicinity of the Premises (whether past or present),
regardless of the source or quantity of any such Release, or (ii) Tenant becomes aware of any regulatory actions, inquiries, inspections, investigations, directives, or any cleanup, compliance, enforcement or abatement proceedings (including
any threatened or contemplated investigations or proceedings) relating to or potentially affecting the Premises, or (iii) Tenant becomes aware of any claims by any person or entity relating to any Hazardous Materials in, on, under, from, about
or in the vicinity of the Premises, whether relating to damage, contribution, cost recovery, compensation, loss or injury. Collectively, the matters set forth in clauses (i), (ii) and (iii) above are hereinafter referred to as
“Hazardous Materials Claims”. Tenant shall promptly forward to Landlord copies of all orders, notices, permits, applications and other communications and reports in connection with any Hazardous Materials Claims. Additionally,
Tenant shall promptly advise Landlord in writing of Tenant’s discovery of any occurrence or condition on, in, under or about the Premises that could subject Tenant or Landlord to any liability, or restrictions on ownership, occupancy,
transferability or use of the Premises under any “Environmental Laws,” as that term is defined below. Tenant shall not enter into any legal proceeding or other action, settlement, consent decree or other compromise with respect to any
Hazardous Materials Claims without first notifying Landlord of Tenant’s intention to do so and affording Landlord the opportunity to join and participate, as a party if Landlord so elects, in such proceedings and in no event shall Tenant enter
into any agreements which are binding on Landlord or the Premises without Landlord’s prior written consent. Landlord shall have the right to appear at and participate in, any and all legal or other administrative proceedings concerning any
Hazardous Materials Claim. For purposes of this Lease, “Environmental Laws” means all applicable present and future laws relating to the protection of human health, safety, wildlife or the environment, including, without limitation,
(i) all requirements pertaining to reporting, licensing, permitting, investigation and/or remediation of emissions, discharges, Releases, or threatened Releases of Hazardous Materials, whether solid, liquid, or gaseous in nature, into the air,
surface water, groundwater, or land, or relating to the manufacture, processing, distribution, use, treatment, storage, disposal, transport, or handling of Hazardous Materials; and (ii) all requirements pertaining to the health and safety of
employees or the public. Environmental Laws include, but are not limited to, the Comprehensive Environmental Response, Compensation and Liability Act of 1980, 42 USC § 9601, et seq., the Hazardous Materials Transportation
Authorization Act of 1994, 49 USC § 5101, et seq., the Solid Waste Disposal Act, as amended by the Resource Conservation and Recovery Act of 1976, and Hazardous and Solid Waste Amendments of 1984, 42 USC § 6901, et
seq., the Federal Water Pollution Control Act, as amended by the Clean Water Act of 1977, 33 USC § 1251, et seq., the Clean Air Act of 1966, 42 USC § 7401, et seq., the Toxic Substances Control Act of 1976, 15 USC
§ 2601, et seq., the Safe Drinking Water Act of 1974, 42 USC §§ 300f through 300j, the Occupational Safety and Health Act of 1970, as amended, 29 USC § 651 et seq., the Oil Pollution Act of 1990,
33 USC § 2701 et seq., the Emergency Planning and Community Right-To-Know Act of 1986, 42 USC § 11001 et seq., the National Environmental
Policy Act of 1969, 42 USC § 4321 et seq., the Federal 

  

					
		  	-14-	  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

 
Insecticide, Fungicide and Rodenticide Act of 1947, 7 USC § 136 et seq., California Carpenter-Presley-Tanner Hazardous Substance Account Act, California Health & Safety
Code §§ 25300 et seq., Hazardous Materials Release Response Plans and Inventory Act, California Health & Safety Code, §§ 25500 et seq., Underground Storage of Hazardous Substances provisions, California Health &
Safety Code, §§ 25280 et seq., California Hazardous Waste Control Law, California Health & Safety Code, §§ 25100 et seq., and any other state or local law counterparts, as amended, as such applicable laws, are in effect
as of the Lease Commencement Date, or thereafter adopted, published, or promulgated. 
 5.3.1.3 Releases of Hazardous
Materials. If, due to the acts or omissions of Tenant or any Tenant’s Agent, any Release of any Hazardous Material in, on, under, from or about the Premises shall occur at any time during the Lease and/or if, due to the acts or
omissions of Tenant or any Tenant’s Agent, any other Hazardous Material condition exists at the Premises that requires response actions of any kind, in addition to notifying Landlord as specified above, Tenant, at its own sole cost and expense,
shall (i) immediately comply with any and all reporting requirements imposed pursuant to any and all Environmental Laws, (ii) provide a written certification to Landlord indicating that Tenant has complied with all applicable reporting
requirements, (iii) take any and all necessary investigation, corrective and remedial action in accordance with any and all applicable Environmental Laws, utilizing an environmental consultant approved by Landlord, all in accordance with the
provisions and requirements of this Section 5.3, including, without limitation, Section 5.3.4, and (iv) take any such additional investigative, remedial and corrective actions as Landlord
shall in its reasonable discretion deem necessary such that the Premises are remediated to the condition existing prior to such Release. 

5.3.1.4 Indemnification. 

5.3.1.4.1 In General. Without limiting in any way Tenant’s obligations under any other provision of this Lease, Tenant
shall be solely responsible for and shall protect, defend, indemnify and hold the Landlord Parties harmless from and against any and all claims, judgments, losses, damages, costs, expenses, penalties, enforcement actions, taxes, fines, remedial
actions, liabilities (including, without limitation, actual attorneys’ fees, litigation, arbitration and administrative proceeding costs, expert and consultant fees and laboratory costs) including, without limitation, consequential damages and
sums paid in settlement of claims, which arise during or after the Lease Term, whether foreseeable or unforeseeable, that arise during or after the Lease Term in whole or in part, foreseeable or unforeseeable, directly or indirectly arising out of
or attributable to the presence, use, generation, manufacture, treatment, handling, refining, production, processing, storage, Release or presence of Hazardous Materials in, on, under or about the Premises by Tenant or Tenant’s Agents. 

5.3.1.4.2 Limitations. Notwithstanding anything to the contrary in this Lease, Tenant shall not be responsible to remediate nor
otherwise be liable or responsible for (nor shall Tenant be responsible to indemnify Landlord with respect to) any Hazardous Materials (A) located in, on, under or about the Project prior to the date of mutual execution of this Lease,
(B) brought upon the Project by Landlord or any Landlord Party(ies), or (C) that have migrated onto the Premises or Project from other properties (“Landlord’s Hazardous Materials“), (except to the extent any of the
Hazardous Materials described in items (A), (B) or (C) are generated, used, transported, exacerbated, released or disturbed, by Tenant or any Tenant Party(ies)). Tenant’s Agent’s shall coordinate with Landlord’s construction and
property team to ensure that any such items described in (A) above are not disturbed by Tenant’s construction activities. To the extent that any Landlord’s Hazardous Materials are discovered at the Project and the remediation of the
same is required a governmental authority with jurisdiction (which remediation is not triggered because of the particular use of the Premises by Tenant or its subtenants or assigns), then Landlord shall remediate the Landlord’s Hazardous
Substances (to the extent required by the applicable governmental authority) at Landlord’s sole cost and expense, and not subject to inclusion in Operating Expenses. 

5.3.1.5 Compliance with Environmental Laws. Without limiting the generality of Tenant’s obligation to comply with
applicable laws as otherwise provided in this Lease, Tenant shall, at its sole cost and expense, comply with all Environmental Laws applicable to its use, or use by any Tenant’s Agents, of any Hazardous Materials. Tenant shall obtain and
maintain any and all necessary permits, licenses, certifications and approvals appropriate or required for the use, handling, storage, and disposal of any Hazardous Materials used, stored, generated, transported, handled, blended, or recycled by
Tenant on the Premises. Landlord shall have a continuing right, without obligation, to require Tenant to obtain, and to review and inspect any and all such permits, licenses, 

  

					
		  	-15-	  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

 
certifications and approvals, together with copies of any and all Hazardous Materials management plans and programs, any and all Hazardous Materials risk management and pollution prevention
programs, and any and all Hazardous Materials emergency response and employee training programs respecting Tenant’s use of Hazardous Materials. If Landlord has reasonable grounds to be concerned that Tenant has failed to comply with the
provisions of this Article 5, upon request of Landlord, Tenant shall deliver to Landlord a narrative description explaining the nature and scope of Tenant’s activities involving Hazardous Materials and showing to Landlord’s
satisfaction compliance with all Environmental Laws and the terms of this Lease. 
 5.3.2 Assurance of Performance. 

5.3.2.1 Environmental Assessments In General. Provided that Landlord gives Tenant no less than five (5) days prior notice
of intended entry and complies with Tenant’s security measures then in effect, Landlord may, but shall not be required to, engage from time to time such contractors as Landlord determines to be appropriate to perform environmental assessments
of a scope reasonably determined by Landlord (an “Environmental Assessment”) to ensure Tenant’s compliance with the requirements of this Lease with respect to Hazardous Materials. 

5.3.2.2 Costs of Environmental Assessments. All costs and expenses incurred by Landlord in connection with any such
Environmental Assessment initially shall be paid by Landlord; provided that if any such Environmental Assessment shows that Tenant has failed to comply with the provisions of this Section 5.3, then all of the reasonable
costs and expenses of such Environmental Assessment shall be reimbursed by Tenant as Additional Rent within thirty (30) days after receipt of written demand therefor, together with documentation of such cost. 

5.3.3 Tenant’s Obligations upon Surrender. At the expiration or earlier termination of the Lease Term, Tenant, at
Tenant’s sole cost and expense, shall: (i) cause an Environmental Assessment of the Premises to be conducted in accordance with Section 15.3; (ii) cause all Hazardous Materials for which Tenant is responsible
under this Lease to be removed from the Premises and disposed of in accordance with all Environmental Laws and as necessary to allow the Premises to be used for purposes consistent with First Class Life Sciences Projects; and (iii) cause
to be removed all containers installed or used by Tenant or Tenant’s Agents to store any Hazardous Materials on the Premises, and cause to be repaired any damage to the Premises caused by such removal. 

5.3.4 Clean-up. 

5.3.4.1 Environmental Reports; Clean-Up. If any written report, including any report
containing results of any Environmental Assessment (an “Environmental Report”) shall indicate (i) the presence of any Hazardous Materials as to which Tenant has a removal or remediation obligation under this
Section 5.3, and (ii) that as a result of same, the investigation, characterization, monitoring, assessment, repair, closure, remediation, removal, or other clean-up (the
“Clean-up”) of any Hazardous Materials is required, Tenant shall immediately prepare and submit to Landlord within thirty (30) days after receipt of the Environmental Report a
comprehensive plan, subject to Landlord’s written approval, not to be unreasonably withheld, conditioned or delayed, specifying the actions to be taken by Tenant to perform the Clean-up so that the
Premises are restored to the conditions required by Environmental Laws and as necessary to allow the Premises to be used in a manner consistent with First Class Life Sciences Projects. Upon Landlord’s approval of the Clean-up plan, Tenant shall, at Tenant’s sole cost and expense, without limitation on any rights and remedies of Landlord under this Lease, immediately implement such plan with a consultant reasonably
acceptable to Landlord and proceed to Clean-up Hazardous Materials in accordance with all applicable laws and as required by such plan and this Lease. If, within thirty (30) days after receiving a copy of
such Environmental Report, Tenant fails either (a) to complete such Clean-up, or (b) with respect to any Clean-up that cannot be completed within such thirty-day period, fails to proceed with diligence to prepare the Clean-up plan and complete the Clean-up as promptly as practicable,
then Landlord shall have the right, but not the obligation, and without waiving any other rights under this Lease, to carry out any Clean-up recommended by the Environmental Report or required by any
governmental authority having jurisdiction over the Premises, and recover all of the costs and expenses thereof from Tenant as Additional Rent, payable within thirty (30) days after receipt of written demand therefor, together with
documentation of such cost. 

  

					
		  	-16-	  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

 5.3.4.2 No Rent Abatement. Tenant shall continue to pay all Rent due or
accruing under this Lease during any Clean-up, and shall not be entitled to any reduction, offset or deferral of any Base Rent or Additional Rent due or accruing under this Lease during any such Clean-up. 
 5.3.4.3 Surrender of Premises. Tenant shall complete any Clean-up prior to surrender of the Premises upon the expiration or earlier termination of this Lease. Tenant shall obtain and deliver to Landlord a letter or other written determination from the overseeing
governmental authority confirming that the Clean-up has been completed in accordance with all requirements of such governmental authority and that no further response action of any kind is required for the
unrestricted use of the Premises in a manner consistent with First Class Life Sciences Projects (“Closure Letter”), unless such governmental authority’s standard practices at the relevant time do not provide for such
Closure Letter. Upon the expiration or earlier termination of this Lease, Tenant shall also be obligated to close all permits obtained in connection with Hazardous Materials in accordance with applicable laws. 

5.3.4.4 Failure to Timely Clean-Up. Should any
Clean-up for which Tenant is responsible not be completed, or should Tenant not receive the Closure Letter (unless such governmental authority’s standard practices at the relevant time do not provide for
such Closure Letter) and any governmental approvals required under Environmental Laws in conjunction with such Clean-up prior to the expiration or earlier termination of this Lease, then Tenant shall be liable
to Landlord as a holdover tenant (as more particularly provided in Article 16) until Tenant has fully complied with its obligations under this Section 5.3. 

5.3.5 Confidentiality. Unless required to do so by applicable law, Tenant agrees that Tenant shall not disclose, discuss,
disseminate or copy any information, data, findings, communications, conclusions and reports regarding the environmental condition of the Premises to any Person (other than Tenant’s consultants, attorneys, property managers and employees that
have a need to know such information), including any governmental authority, without the prior written consent of Landlord. In the event Tenant reasonably believes that disclosure is required by applicable law, it shall provide Landlord ten
(10) days’ advance notice of disclosure of confidential information so that Landlord may attempt to obtain a protective order. Tenant may additionally release such information to bona fide prospective purchasers, lenders, assignees or
subtenants, subject to any such parties’ written agreement to be bound by the terms of this Section 5.3. 

5.3.6 Copies of Environmental Reports. Within thirty (30) days of receipt thereof, Tenant shall provide Landlord with a copy
of any and all environmental assessments, audits, studies and reports in Tenant’s possession regarding Tenant’s activities with respect to the Premises, or ground water beneath the Land, or the environmental condition or Clean-up thereof. Tenant shall be obligated to provide Landlord with a copy of such materials without regard to whether such materials are generated by Tenant or prepared for Tenant, or how Tenant comes into
possession of such materials, unless to do so would expose Tenant to a claim of breach of a nondisclosure obligation or be a violation of applicable law. 

5.3.7 Intentionally Omitted. 

5.3.8 Signs, Response Plans, Etc. Tenant shall be responsible for posting on the Premises any signs required under applicable
Environmental Laws. Tenant shall also complete and file any business response plans or inventories required by any applicable laws. Tenant shall concurrently file a copy of any such business response plan or inventory with Landlord. 

5.3.9 Survival. Each covenant, agreement, representation, warranty and indemnification made by Tenant set forth in this
Section 5.3 shall survive the expiration or earlier termination of this Lease and shall remain effective until all of Tenant’s obligations under this Section 5.3 have been completely performed
and satisfied. 
 6. SERVICES AND UTILITIES 

6.1 In General. 

6.1.1 Subject to limitations imposed by all governmental rules, regulations and guidelines applicable thereto, Landlord shall provide heating,
ventilation and air conditioning (“HVAC”) for normal comfort for 

  

					
		  	-17-	  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

 
Tenant’s use of the Premises for office use, on a basis of twenty (24) hours per day, seven (7) days per week. Tenant shall cooperate fully with Landlord at all times and abide by
all regulations and requirements that Landlord may reasonably prescribe for the proper functioning and protection of the HVAC, electrical, mechanical and plumbing systems. 

6.1.2 Landlord shall provide reasonably sufficient electricity to the Premises in a manner consistent with the electricity provided to the
Building prior to the date of this Lease, which shall generally be available twenty-four (24) hours per day, seven (7) days per week, every day of the year. Tenant shall pay for all utilities (including without limitation, electricity,
gas, sewer and water) attributable to its use of the entire Premises, and shall also provide its own janitorial and security services for the Building. Such utility use shall include electricity, water, and gas use for lighting, incidental use and
“HVAC,” as that term is defined above. 
 6.1.3 Landlord shall not provide janitorial services for the Premises. Tenant shall be
solely responsible for performing all janitorial services and other cleaning of the Premises, all in compliance with applicable laws. The janitorial and cleaning of the Premises shall be adequate to maintain the Premises in a manner consistent with
First Class Life Sciences Projects. 
 6.1.4 Subject to applicable laws, Section 27 of this Lease and other
provisions of this Lease, and except in the event of an emergency, Tenant shall have access to the Building, the Premises and the common areas of the Building, other than common areas requiring access with a Building engineer, twenty-four
(24) hours per day, seven (7) days per week, every day of the year. 
 6.1.5 All other utilities (including without limitation,
gas, phone/data, sewer and water) shall be paid directly by Tenant to the applicable utility provider (or in the case on common metered utilities, to Landlord based on Landlord’s reasonable determination of Tenant’s use), and Landlord
shall cooperate with all reasonable requirements of utility providers so as to ensure service is available to the Premises. 
 6.1.6 If
Tenant requests any such additional services, then Tenant shall pay to Landlord the cost of such additional services, including Landlord’s standard fee as Landlord may from time to time reasonably establish for the tenants of the Building
generally for its involvement with such additional services, promptly upon being billed for same. 
 Tenant shall cooperate fully with
Landlord at all times and abide by all regulations and requirements that Landlord may reasonably prescribe for the proper functioning and protection of the HVAC, electrical, mechanical and plumbing systems. 

6.2 Interruption of Use. Tenant agrees that Landlord shall not be liable for damages, by abatement of Rent (except as set forth
in Section 19.5.2, below) or otherwise, for failure to furnish or delay in furnishing any service (including telephone and telecommunication services), or for any diminution in the quality or quantity thereof, when such
failure or delay or diminution is occasioned, in whole or in part, by breakage, repairs, replacements, or improvements, by any strike, lockout or other labor trouble, by inability to secure electricity, gas, water, or other fuel at the Building or
Project after reasonable effort to do so, by any riot or other dangerous condition, emergency, accident or casualty whatsoever, by act or default of Tenant or other parties, or by any other cause; and such failures or delays or diminution shall
never be deemed to constitute an eviction or disturbance of Tenant’s use and possession of the Premises or relieve Tenant from paying Rent (except as set forth in Section 19.5.2, below) or performing any of its
obligations under this Lease. Furthermore, Landlord shall not be liable under any circumstances for a loss of, or injury to, property or for injury to, or interference with, Tenant’s business, including, without limitation, loss of profits,
however occurring, through or in connection with or incidental to a failure to furnish any of the services or utilities as set forth in this Article 6. 

6.3 Emergency Generator. 

6.3.1 Existing Emergency Generator. Landlord and Tenant hereby acknowledge that there is an existing generator currently serving
the Premises (“Emergency Generator”), and Tenant shall have the right to connect to the Emergency Generator for up to Tenant’s Share of the electrical capacity provided by such Emergency

  

					
		  	-18-	  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

 
Generator. Tenant’s use of the Emergency Generator shall be at Tenant’s sole risk. Landlord represents that the Emergency Generator is currently in place and shall be in good operating
condition on the Lease Commencement Date, and during the Lease Term Landlord shall maintain the Generator in good condition and repair, and Tenant shall be responsible for a share of the costs of such maintenance and repair based on the proportion
of the Generator capacity allocated to the Premises. Tenant hereby waives any claims against Landlord or any Landlord Parties resulting from Tenant’s use of the Emergency Generator, or any failure of the Emergency Generator to operate as
designed, and agrees that Landlord shall not be liable for any damages resulting from any failure in operation of the Emergency Generator, including, without limitation any injury or damage to, or interference with, Tenant’s business, including
but not limited to, loss of profits, loss of rents or other revenues, loss of business opportunity, loss of goodwill or loss of use, or loss to equipment, inventory, scientific research, scientific experiments, laboratory animals, products,
specimens, samples, and/or scientific, business, accounting and other records of every kind and description kept at the Premises and any and all income derived or derivable therefrom. Tenant acknowledges that Operating Expenses shall include
Landlord’s costs incurred in maintaining and operating the Emergency Generator (including all permit costs and fees). 
 6.3.2
Tenant’s Emergency Generator. In the event Tenant wishes to install a separate generator to provide back-up generator services to the Premises instead of the existing Emergency Generator,
subject to the receipt of all necessary approvals from the applicable governmental authority, Tenant shall have the right to install a back-up generator in the Premises, or outside the Premises in the location
reasonably designated by Landlord (subject to the same being approved by the city), as an Alteration (in which case such installation shall be governed by the terms of Article 8) (the “Tenant Generator”). Tenant
acknowledges that Landlord has not made any representation regarding the receipt of approvals for the Tenant Generator, and if Tenant is unable for any reason to receive such approvals, Landlord shall not be liable for any damages resulting
therefrom. In the event such Tenant Generator is installed, then during the Lease Term, Tenant shall maintain such Tenant Generator at Tenant’s sole cost and expense. Notwithstanding the foregoing, Landlord shall not be liable for any damages
whatsoever resulting from any failure in operation of the Tenant Generator, or the failure of the Tenant Generator to provide suitable or adequate back-up power to the Premises, including but not limited to,
loss of profits, loss of rents or other revenues, loss of business opportunity, loss of goodwill or loss of use, in each case, however occurring, or loss to inventory, scientific research, scientific experiments, laboratory animals, products,
specimens, samples, and/or scientific, business, accounting and other records of every kind and description kept at the Premises and any and all income derived or derivable therefrom. Tenant’s obligations with respect to the Premises, including
the insurance and indemnification obligations contained in Article 10, below, shall apply to Tenant’s use of the Tenant Generator and Tenant shall carry industry standard Boiler and machinery insurance covering the
Tenant Generator. Tenant shall maintain all required permits in connection with the Tenant Generator throughout the Lease Term. If installed, at Landlord’s election prior to the expiration or earlier termination of this Lease, Tenant shall
either (A) leave the Tenant Generator in place, in which event Tenant shall surrender the Generator (and shall transfer to Landlord all permits maintained by Tenant in connection with the Generator during the Lease Term) concurrent with the
surrender of the Premises to Landlord as required hereunder in good operating and working order, with all permits current, or (B) remove the Tenant Generator prior to the expiration or earlier termination of this Lease, and repair all damage to
the Building and Premises resulting from such removal, at Tenant’s sole cost and expense. In the event that Landlord fails to expressly elect to have the Tenant Generator left in place upon the expiration or earlier termination of this Lease,
then Landlord shall be deemed to have elected to have Tenant remove such Tenant Generator. 
 7. REPAIRS 

7.1 Tenant Repair Obligations. Tenant shall, at Tenant’s own expense, keep the interior,
non-structural elements of the Premises, including all improvements, fixtures, furnishings, and systems and equipment therein (including, without limitation, plumbing fixtures and equipment such as
dishwashers, garbage disposals, and insta-hot dispensers), and the floor or floors of the Building on which the Premises are located (but not including the structural elements of such floors), in good order,
repair and condition at all times during the Lease Term (“Tenant’s Repair Obligations”). In addition, Tenant shall, at Tenant’s own expense, and within any reasonable period of time specified by Landlord, promptly and
adequately repair all damage to the Premises and replace or repair all damaged, broken, or worn fixtures and appurtenances, except for damage caused by ordinary wear and tear or beyond the reasonable control of Tenant; provided however, that if
Tenant fails to make such repairs following notice and a reasonable opportunity to cure, Landlord may, but need not, make such repairs and replacements, and Tenant shall 

  

					
		  	-19-	  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

 
pay Landlord the cost thereof, including a percentage of the cost thereof (to be uniformly established for the Building and/or the Project but not to exceed 10% of the total cost of the repair)
sufficient to reimburse Landlord for all overhead, general conditions, fees and other costs or expenses arising from Landlord’s involvement with such repairs and replacements forthwith upon being billed for same. 

7.2 Landlord’s Right to Perform Tenant’s Repair Obligations. Tenant shall notify Landlord in writing at least thirty
(30) days prior to performing any Tenant’s Repair Obligation which affects the Building Systems or which is reasonably anticipated to cost more than $50,000.00 (a “Material Tenant Repair”). Upon receipt of such notice from
Tenant, Landlord shall have the right to either (i) perform such Material Tenant Repair by delivering notice of such election to Tenant within thirty (30) days following receipt of Tenant’s notice, and Tenant shall pay Landlord the
cost thereof (including Landlord’s reasonable supervision fee pursuant to Section 7.1) within thirty (30) days after receipt of an invoice therefor, or (ii) require Tenant to perform such Material Tenant
Repair at Tenant’s sole cost and expense. If Tenant fails to perform any Tenant’s Repair Obligation within a reasonable time period following notice from Landlord, as reasonably determined by Landlord, then Landlord may, but need not,
following delivery of notice to Tenant of such election, make such Tenant Repair Obligation, and Tenant shall pay Landlord the cost thereof, (including Landlord’s reasonable supervision fee pursuant to Section 7.1)
within thirty (30) days after receipt of an invoice therefor. 
 7.3 Landlord Repair Obligations. Landlord shall be
responsible for repairs to the exterior walls, foundation and roof (including roof membrane) of the Building, the structural portions of the floors of the Building, and the load bearing walls, windows and plate glass (the “Building
Structure”), and the core plumbing, fire sprinkler system, heating, ventilating, air conditioning, elevator, and electrical systems installed or furnished by Landlord (the “Building Systems”), except to the extent that such
repairs are required due to the negligence or willful misconduct of Tenant; provided, however, that if such repairs are due to the negligence or willful misconduct of Tenant, Landlord shall nevertheless make such repairs at Tenant’s expense,
or, if covered by Landlord’s insurance, Tenant shall only be obligated to pay any deductible in connection therewith. Subject to the terms of Article 27, below, Landlord may, but shall not be required to, enter the
Premises at all reasonable times to make such repairs, alterations, improvements or additions to the Premises or to the Project or to any equipment located in the Project as Landlord shall desire or deem necessary or as Landlord may be required to
do by governmental or quasi-governmental authority or court order or decree. Tenant hereby waives any and all rights under and benefits of subsection 1 of Section 1932 and Sections 1941 and 1942 of the California Civil Code or under any similar
law, statute, or ordinance now or hereafter in effect. The Building Systems and the Building Structure shall collectively be known as the “Base Building.” 

8. ADDITIONS AND ALTERATIONS 
 8.1
Landlord’s Consent to Alterations. Tenant may not make any improvements, alterations, additions or changes to the Premises or any mechanical, plumbing or HVAC facilities or systems pertaining to the Premises (collectively, the
“Alterations”) without first procuring the prior written consent of Landlord to such Alterations, which consent shall be requested by Tenant not less than thirty (30) days prior to the commencement thereof, and which consent
shall not be unreasonably withheld, conditioned or delayed by Landlord, provided it shall be deemed reasonable for Landlord to withhold its consent to any Alteration which adversely affects the Base Building or is visible from the exterior of the
Building. Notwithstanding the foregoing, Tenant shall be permitted to make Alterations following ten (10) business days’ notice to Landlord, but without Landlord’s prior consent, to the extent that such Alterations (i) do not
affect the Base Building, (ii) are not visible from the exterior of the Building, (iii) cost less than $50,000.00 for a particular job of work, and (iv) do not lower the value of the Premises (e.g., by converting lab space to office
space). The construction of the initial improvements to the Premises shall be governed by the terms of the Tenant Work Letter and not the terms of this Article 8. 

8.2 Manner of Construction. Landlord may impose, as a condition of its consent to any and all Alterations or repairs of the
Premises or about the Premises, such requirements as Landlord in its reasonable discretion may deem desirable, including, but not limited to, the requirement that upon Landlord’s request, Tenant shall, at Tenant’s expense, remove such
Alterations upon the expiration or any early termination of the Lease Term. Tenant shall construct such Alterations and perform such repairs in a good and workmanlike manner, in conformance with any and all applicable federal, state, county or
municipal laws, rules and regulations and pursuant to a valid building permit, issued by the city in which the Building is located (or other applicable governmental authority). Tenant shall 

  

					
		  	-20-	  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

 
not use (and upon notice from Landlord shall cease using) contractors, services, workmen, labor, materials or equipment that, in Landlord’s reasonable judgment, would disturb labor harmony
with the workforce or trades engaged in performing other work, labor or services in or about the Building or the Common Areas. Upon completion of any Alterations (or repairs), Tenant shall deliver to Landlord final lien waivers from all contractors,
subcontractors and materialmen who performed such work. In addition to Tenant’s obligations under Article 9 of this Lease, upon completion of any Alterations, Tenant agrees to cause a Notice of Completion to be recorded in the office of
the Recorder of the County of San Diego in accordance with Section 3093 of the Civil Code of the State of California or any successor statute, and Tenant shall deliver to the Project construction manager a reproducible copy of the “as
built” drawings of the Alterations as well as all permits, approvals and other documents issued by any governmental agency in connection with the Alterations. 

8.3 Payment for Improvements. If Tenant orders any work directly from Landlord, Tenant shall pay to Landlord an amount equal to
five percent (5%) of the hard costs of such work to compensate Landlord for all overhead, general conditions, fees and other costs and expenses arising from Landlord’s involvement with such work. If Tenant does not order any work directly from
Landlord, Tenant shall reimburse Landlord for Landlord’s reasonable, actual, out-of-pocket costs and expenses actually incurred in connection with Landlord’s
review of such work, not to exceed five thousand dollars ($5,000). 
 8.4 Construction Insurance. In addition to the
requirements of Article 10 of this Lease, in the event that Tenant makes any Alterations, prior to the commencement of such Alterations, Tenant shall provide Landlord with evidence that Tenant carries “Builder’s All
Risk” insurance in an amount approved by Landlord covering the construction of such Alterations, and such other insurance as Landlord may reasonably require, it being understood and agreed that all of such Alterations shall be insured by
Tenant pursuant to Article 10 of this Lease immediately upon completion thereof. In addition, Tenant’s contractors and subcontractors shall be required to carry (i) Commercial General Liability Insurance in an amount approved by
Landlord, with Landlord, and, at Landlord’s option, Landlord’s property manager and project manager, as additional insureds in an amount approved by Landlord, and otherwise in accordance with the requirements of Article 10 of this Lease,
and (ii) workers compensation insurance with a waiver of subrogation in favor of Landlord . Landlord may, in its discretion, require Tenant to obtain a lien and completion bond or some alternate form of security satisfactory to Landlord in an
amount sufficient to ensure the lien-free completion of such Alterations and naming Landlord as a co-obligee, but only if the aggregate cost of such work is expected to exceed $100,000.00. 

8.5 Landlord’s Property. All Alterations, improvements, fixtures, equipment and/or appurtenances which may be installed or
placed in or about the Premises, from time to time, shall be at the sole cost of Tenant and shall be and become the property of Landlord and remain in place at the Premises following the expiration or earlier termination of this Lease.
Notwithstanding the foregoing, Landlord may, by written notice to Tenant at the time Landlord consents to such Alteration (or with respect to Alterations not requiring Landlord consent, upon Tenant’s request for a determination), require
Tenant, at Tenant’s expense, to remove any Alterations within the Premises and to repair any damage to the Premises and Building caused by such removal and return the affected portion of the Premises to a building standard tenant improved
condition as reasonably determined by Landlord. If Tenant fails to complete such removal and/or to repair any damage caused by the removal of any Alterations and return the affected portion of the Premises to a building standard tenant improved
condition as reasonably determined by Landlord, Landlord may do so and may charge the cost thereof to Tenant. Tenant hereby protects, defends, indemnifies and holds Landlord harmless from any liability, cost, obligation, expense or claim of lien in
any manner relating to the installation, placement, removal or financing of any such Alterations, improvements, fixtures and/or equipment in, on or about the Premises, which obligations of Tenant shall survive the expiration or earlier termination
of this Lease. Notwithstanding anything to the contrary in this Lease, Tenant shall not be required to remove any of the Tenant Improvements upon the expiration or earlier termination of this Lease. 

9. COVENANT AGAINST LIENS Tenant shall keep the Project and Premises free from any liens or encumbrances arising out of the work performed, materials
furnished or obligations incurred by or on behalf of Tenant (except where the lien or encumbrance arises from Landlord’s failure to pay timely amounts due from Landlord including the amounts payable by Landlord with respect to the Tenant
Improvements), and shall protect, defend, indemnify and hold Landlord harmless from and against any claims, liabilities, judgments or costs (including, without limitation, reasonable attorneys’ fees and costs) arising out of same or in
connection therewith. Tenant shall give 

  

					
		  	-21-	  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

 
Landlord notice at least ten(10) business days prior to the commencement of any such work on the Premises (or such additional time as may be necessary under applicable laws) to afford Landlord
the opportunity of posting and recording appropriate notices of non-responsibility (to the extent applicable pursuant to then applicable laws). Tenant shall remove any such lien or encumbrance by bond or
otherwise within ten (10) business days after notice by Landlord, and if Tenant shall fail to do so, Landlord may pay the amount necessary to remove such lien or encumbrance, without being responsible for investigating the validity thereof.

 10. INSURANCE 
 10.1
Indemnification and Waiver. Except to the extent arising from the gross negligence or willful misconduct of Landlord or the Landlord Parties, Tenant hereby assumes all risk of damage to property or injury to persons in, upon or about
the Premises from any cause whatsoever and agrees that Landlord, its partners, subpartners and their respective officers, agents, servants, employees, lenders, any property manager and independent contractors (collectively, “Landlord
Parties”) shall not be liable for, and are hereby released from any responsibility for, any damage either to person or property or resulting from the loss of use thereof, which damage is sustained by Tenant or by other persons claiming
through Tenant. Tenant shall indemnify, defend, protect, and hold harmless the Landlord Parties from any and all claims, loss, cost, damage, injury, expense and liability (including without limitation court costs and reasonable attorneys’ fees)
incurred in connection with or arising from any cause in, on or about the Premises, any acts, omissions or negligence of Tenant or of any person claiming by, through or under Tenant, or of the contractors, agents, servants, employees, invitees,
guests or licensees of Tenant or any such person, in, on or about the Project or any breach of the terms of this Lease, either prior to, during, or after the expiration of the Lease Term, except to the extent arising from the gross negligence or
willful misconduct of Landlord or any of the Landlord Parties. Landlord shall indemnify, defend, protect, and hold harmless Tenant or any person claiming by, through or under Tenant , or of the directors, officers, representatives contractors,
agents, servants, employees, invitees, guests, or licensees of Tenant (collectively, “Tenant Parties”) from any and all claims, loss, cost, damage, injury, expense and liability (including without limitation court costs and
reasonable attorneys’ fees) incurred in connection with or arising from any cause in, on or about the Premises, any acts, omissions or negligence of Landlord or of any person claiming by, through or under Landlord, or of the contractors,
agents, servants, employees, invitees, guests or licensees of Landlord or any such person, in, on or about the Project or any breach of the terms of this Lease, either prior to, during, or after the expiration of the Lease Term, except to the extent
arising from the gross negligence or willful misconduct of Tenant or any of the Tenant Parties. Should Landlord or Tenant be named as a defendant in any suit brought against the other subject to the indemnification in this
Section 10.1, the indemnifying party shall pay to the other party such other party’s costs and expenses incurred in such suit, including without limitation, its actual professional fees such as reasonable
appraisers’, accountants’ and attorneys’ fees. The provisions of this Section 10.1 shall survive the expiration or sooner termination of this Lease with respect to any claims or liability arising in
connection with any event occurring prior to such expiration or termination. 
 10.2 Tenant’s Compliance With Landlord’s
Property Insurance. Landlord shall insure the Building during the Lease Term against loss or damage under an “all risk” property insurance policy. Such coverage shall be in such coverage and deductible amounts, from such companies,
and on such other terms and conditions, as Landlord may from time to time reasonably determine. Additionally, at the option of Landlord, such insurance coverage may include the risks of earthquakes and/or flood damage and additional hazards, a
rental loss endorsement and one or more loss payee endorsements as required by, and in favor of, the holders of any mortgages or deeds of trust encumbering the interest of Landlord in the Building or the ground or underlying lessors of the Building,
or any portion thereof. Tenant shall, at Tenant’s expense, comply with all insurance company requirements pertaining to the use of the Premises. If Tenant’s conduct or use of the Premises causes any increase in the premium for such
insurance policies then Tenant shall reimburse Landlord for any such increase. Tenant, at Tenant’s expense, shall comply with all rules, orders, regulations or requirements of the American Insurance Association (formerly the National Board of
Fire Underwriters) and with any similar body. Tenant shall also provide Landlord and Landlord’s insurer(s) with such information regarding the use of the Premises and any damage to the Premises as they may require in connection with the
placement of insurance for the Premises or the adjusting of any losses to the Premises. 
 10.3 Tenant’s Insurance. Tenant
shall maintain the following coverages in the following amounts. 

  

					
		  	-22-	  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

 10.3.1 Commercial General Liability Insurance on an occurrence form covering the insured
against claims of bodily injury, personal injury and property damage (including loss of use thereof) arising out of Tenant’s operations, and contractual liabilities including a contractual coverage, and including products and completed
operations coverage, for limits of liability on a per location basis of not less than: 
  

			
	Bodily Injury and
Property Damage Liability	  	 $2,000,000 each occurrence
 $3,000,000 annual
aggregate

		
	Personal Injury Liability	  	$2,000,000 each occurrence
$2,000,000 annual aggregate

 Any combination of primary and excess/umbrella liability policies may be utilized in order to meet the limit
requirements above. 
 10.3.2 Property Insurance covering (i) all office furniture, business and trade fixtures, office equipment,
free-standing cabinet work, movable partitions, merchandise and all other items of Tenant’s property on the Premises installed by, for, or at the expense of Tenant, (ii) the Tenant Improvements and any other improvements which exist in the
Premises as of the Lease Commencement Date (excluding the Base Building) (the “Original Improvements”), and (iii) all other improvements, alterations and additions to the Premises. Such insurance shall be written on an
“all risks” of physical loss or damage basis, for the full replacement cost value (subject to reasonable deductible amounts) new without deduction for depreciation of the covered items and in amounts that meet any co-insurance clauses of the policies of insurance and shall include coverage for damage or other loss caused by fire or other peril including, but not limited to, vandalism and malicious mischief, theft, water
damage of any type, including sprinkler leakage, bursting or stoppage of pipes, and explosion. 
 10.3.3 Business Income Interruption for one
(1) year plus Extra Expense insurance in such amounts as will reimburse Tenant for actual direct or indirect loss of earnings attributable to the risks outlined in Section 10.3.2 above. 

10.3.4 Worker’s Compensation and Employer’s Liability or other similar insurance pursuant to all applicable state and local statutes
and regulations. The policy shall include a waiver of subrogation in favor of Landlord, its employees, Lenders and any property manager or partners. 

10.4 Form of Policies. The minimum limits of policies of insurance required of Tenant under this Lease shall in no event limit
the liability of Tenant under this Lease. Such insurance shall (i) name Landlord, its subsidiaries and affiliates, its property manager (if any) and any other party the Landlord so specifies, as an additional insured or loss payee, as
applicable, including Landlord’s managing agent, if any; (ii) be issued by an insurance company having a rating of not less than A:IX in Best’s Insurance Guide or which is otherwise acceptable to Landlord and licensed to do business
in the State of California; (iv) be primary insurance as to all claims thereunder and provide that any insurance carried by Landlord is excess and is non-contributing with any insurance required of
Tenant; (v) be in form and content reasonably acceptable to Landlord; and (vi) provide that said insurance shall not be canceled or coverage changed unless thirty (30) days’ prior written notice shall have been given to Landlord
and any mortgagee of Landlord (unless such cancellation is the result of non-payment of premiums). Tenant shall deliver certificates thereof to Landlord on or before the Lease Commencement Date and at least
ten (10) days before the expiration dates thereof. In the event Tenant shall fail to procure such insurance, or to deliver such policies or certificate, Landlord may, at its option, procure such policies for the account of Tenant, and the cost
thereof shall be paid to Landlord within five (5) days after delivery to Tenant of bills therefor. 
 10.5 Subrogation.
Landlord and Tenant hereby agree to look solely to, and seek recovery only from, their respective insurance carriers in the event of a property or business interruption loss to the extent that such coverage is agreed to be provided hereunder. The
parties each hereby waive all rights and claims against each other for such losses, and waive all rights of subrogation of their respective insurers, provided such waiver of subrogation shall not affect the right to the insured to recover
thereunder. The parties agree that their respective insurance policies do now, or shall, contain the waiver of subrogation. 

  

					
		  	-23-	  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

 10.6 Additional Insurance Obligations. Tenant shall carry and maintain during
the entire Lease Term, at Tenant’s sole cost and expense, increased amounts of the insurance required to be carried by Tenant pursuant to this Article 10 and such other reasonable types of insurance coverage and in such reasonable
amounts covering the Premises and Tenant’s operations therein, as may be reasonably requested by Landlord or Landlord’s lender, but in no event in excess of the amounts and types of insurance then being required by landlords of buildings
comparable to and in the vicinity of the Building. 
 11. DAMAGE AND DESTRUCTION 

11.1 Repair of Damage to Premises by Landlord. Tenant shall promptly notify Landlord of any damage to the Premises resulting from
fire or any other casualty. If the Premises or any Common Areas serving or providing access to the Premises shall be damaged by fire or other casualty, Landlord shall promptly and diligently, subject to reasonable delays for insurance adjustment or
other matters beyond Landlord’s reasonable control, and subject to all other terms of this Article 11, restore the Base Building and such Common Areas. Such restoration shall be to substantially the same condition of the Base Building
and the Common Areas prior to the casualty, except for modifications required by zoning and building codes and other laws or by the holder of a mortgage on the Building or Project or any other modifications to the Common Areas deemed desirable by
Landlord, which are consistent with the character of the Project, provided that access to the Premises shall not be materially impaired. Upon the occurrence of any damage to the Premises, upon notice (the “Landlord Repair Notice”)
to Tenant from Landlord, Tenant shall assign to Landlord (or to any party designated by Landlord) all insurance proceeds payable to Tenant under Tenant’s insurance required under Section 10.3.2(ii) and (iii) of
this Lease, and Landlord shall repair any injury or damage to the Tenant Improvements and the Original Improvements installed in the Premises and shall return such Tenant Improvements and Original Improvements to their original condition; provided
that if the cost of such repair by Landlord exceeds the amount of insurance proceeds received by Landlord from Tenant’s insurance carrier (including by taking into account any deductible or self-insured retention), as assigned by Tenant, the
cost of such repairs shall be paid by Tenant to Landlord prior to Landlord’s commencement of repair of the damage. In the event that Landlord does not deliver the Landlord Repair Notice within sixty (60) days following the date the
casualty becomes known to Landlord, Tenant shall, at its sole cost and expense, repair any injury or damage to the Tenant Improvements and the Original Improvements installed in the Premises and shall return such Tenant Improvements and Original
Improvements to their original condition. Whether or not Landlord delivers a Landlord Repair Notice, prior to the commencement of construction, Tenant shall submit to Landlord, for Landlord’s review and approval, all plans, specifications and
working drawings relating thereto, and Landlord shall select the contractors to perform such improvement work. Tenant shall in addition cooperate with requests for information regarding any repairs from Landlord’s insurer(s) by providing the
requested information within ten (10) days after Tenant receives the request. Landlord shall not be liable for any inconvenience or annoyance to Tenant or its visitors, or injury to Tenant’s business resulting in any way from such damage
or the repair thereof; provided however, that if such fire or other casualty shall have damaged the Premises or Common Areas necessary to Tenant’s occupancy, and the Premises are not occupied by Tenant as a result thereof, then during the time
and to the extent the Premises are unfit for occupancy, the Rent shall be abated in proportion to the ratio that the amount of rentable square feet of the Premises which is unfit for occupancy for the purposes permitted under this Lease bears to the
total rentable square feet of the Premises. In the event that Landlord shall not deliver the Landlord Repair Notice, Tenant’s right to rent abatement pursuant to the preceding sentence shall terminate as of the date which is reasonably
determined by Landlord to be the date Tenant should have completed repairs to the Premises assuming Tenant used reasonable due diligence in connection therewith. 

11.2 Landlord’s Option to Repair. Notwithstanding the terms of Section 11.1 of this Lease,
Landlord may elect not to rebuild and/or restore the Premises, Building and/or Project, and instead terminate this Lease, by notifying Tenant in writing of such termination within sixty (60) days after the date of discovery of the damage, such
notice to include a termination date giving Tenant sixty (60) days to vacate the Premises, but Landlord may so elect only if the Building or Project shall be damaged by fire or other casualty or cause, whether or not the Premises are affected,
and one or more of the following conditions is present: (i) in Landlord’s reasonable judgment, repairs cannot reasonably be completed within one hundred eighty (180) days after the date of discovery of the damage (when such repairs
are made without the payment of overtime or other premiums); (ii) the holder of any mortgage on the Building or Project or ground lessor with respect to the Building or Project shall require that the insurance proceeds or any portion thereof be used
to retire the mortgage debt, or shall terminate the ground lease, as the case may be; (iii) the 

  

					
		  	-24-	  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

 
damage is not fully covered by Landlord’s insurance policies (unless such shortfall is a result of Landlord’s failure to maintain the insurance that Landlord is required to maintain
pursuant to Section 10.2 above); (iv) material damage occurs during the last twelve (12) months of the Lease Term; or (v) any owner of any other portion of the Project, other than Landlord, does not intend to
repair the damage to such portion of the Project; provided, however, that if Landlord does not elect to terminate this Lease pursuant to Landlord’s termination right as provided above, and the repairs cannot, in the reasonable opinion of
Landlord, be completed within one hundred eighty (180) days after being commenced, Tenant may elect, no later than sixty (60) days after receipt of the Landlord Repair Notice, to terminate this Lease by written notice to Landlord effective
as of the date specified in the notice, which date shall not be less than thirty (30) days nor more than sixty (60) days after the date such notice is given by Tenant. Notwithstanding the provisions of this
Section 11.2, Tenant shall have the right to terminate this Lease under this Section 11.2 only if each of the following conditions is satisfied: (a) the damage to the Project by fire or other
casualty was not caused by the gross negligence or intentional act of Tenant or any of the Tenant Parties; (b) no Event of Default has occurred and is continuing; (c) as a result of the damage, Tenant cannot reasonably conduct business
from the Premises; and, (d) as a result of the damage to the Project, Tenant does not occupy or use the Premises. 
 11.3 Waiver
of Statutory Provisions. The provisions of this Lease, including this Article 11, constitute an express agreement between Landlord and Tenant with respect to any and all damage to, or destruction of, all or any part of the Premises,
the Building or the Project, and any statute or regulation of the State of California, including, without limitation, Sections 1932(2) and 1933(4) of the California Civil Code, with respect to any rights or obligations concerning damage or
destruction in the absence of an express agreement between the parties, and any other statute or regulation, now or hereafter in effect, shall have no application to this Lease or any damage or destruction to all or any part of the Premises, the
Building or the Project. 
 12. NONWAIVER No provision of this Lease shall be deemed waived by either party hereto unless expressly
waived in a writing signed thereby. The waiver by either party hereto of any breach of any term, covenant or condition herein contained shall not be deemed to be a waiver of any subsequent breach of same or any other term, covenant or condition
herein contained. The subsequent acceptance of Rent hereunder by Landlord shall not be deemed to be a waiver of any preceding breach by Tenant of any term, covenant or condition of this Lease, other than the failure of Tenant to pay the particular
Rent so accepted, regardless of Landlord’s knowledge of such preceding breach at the time of acceptance of such Rent. No acceptance of a lesser amount than the Rent herein stipulated shall be deemed a waiver of Landlord’s right to receive
the full amount due, nor shall any endorsement or statement on any check or payment or any letter accompanying such check or payment be deemed an accord and satisfaction, and Landlord may accept such check or payment without prejudice to
Landlord’s right to recover the full amount due. No receipt of monies by Landlord from Tenant after the termination of this Lease shall in any way alter the length of the Lease Term or of Tenant’s right of possession hereunder, or after
the giving of any notice shall reinstate, continue or extend the Lease Term or affect any notice given Tenant prior to the receipt of such monies, it being agreed that after the service of notice or the commencement of a suit, or after final
judgment for possession of the Premises, Landlord may receive and collect any Rent due, and the payment of said Rent shall not waive or affect said notice, suit or judgment. 

  

					
		  	-25-	  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

 13. CONDEMNATION If the whole or any part of the Premises, Building or Project shall be taken
by power of eminent domain or condemned by any competent authority for any public or quasi-public use or purpose, or if any adjacent property or street shall be so taken or condemned, or reconfigured or vacated by such authority in such manner as to
require the use, reconstruction or remodeling of any part of the Premises, Building or Project, or if Landlord shall grant a deed or other instrument in lieu of such taking by eminent domain or condemnation, Landlord shall have the option to
terminate this Lease effective as of the date possession is required to be surrendered to the authority. If more than twenty-five percent (25%) of the rentable square feet of the Premises is taken, or if access to the Premises is substantially
impaired, in each case for a period in excess of one hundred eighty (180) days, Tenant shall have the option to terminate this Lease effective as of the date possession is required to be surrendered to the authority. Tenant shall not because of
such taking assert any claim against Landlord or the authority for any compensation because of such taking and Landlord shall be entitled to the entire award or payment in connection therewith, except that Tenant shall have the right to file any
separate claim available to Tenant for any taking of Tenant’s personal property and fixtures belonging to Tenant and removable by Tenant upon expiration of the Lease Term pursuant to the terms of this Lease, and for moving expenses, so long as
such claims do not diminish the award available to Landlord, its ground lessor with respect to the Building or Project or its mortgagee, and such claim is payable separately to Tenant. All Rent shall be apportioned as of the date of such
termination. If any part of the Premises shall be taken, and this Lease shall not be so terminated, the Rent shall be proportionately abated. Tenant hereby waives any and all rights it might otherwise have pursuant to Section 1265.130 of The
California Code of Civil Procedure. Notwithstanding anything to the contrary contained in this Article 13, in the event of a temporary taking of all or any portion of the Premises for a period of one hundred and eighty (180) days or less, then
this Lease shall not terminate but the Base Rent and the Additional Rent shall be abated for the period of such taking in proportion to the ratio that the amount of rentable square feet of the Premises taken bears to the total rentable square feet
of the Premises. Landlord shall be entitled to receive the entire award made in connection with any such temporary taking. 
 14. ASSIGNMENT AND
SUBLETTING 
 14.1 Transfers. Except in connection with a Permitted Transfer (as that term is defined in
Section 14.8 below), Tenant shall not, without the prior written consent of Landlord, assign, mortgage, pledge, hypothecate, encumber, or permit any lien to attach to, or otherwise transfer, this Lease or any interest hereunder, permit
any assignment, or other transfer of this Lease or any interest hereunder by operation of law, sublet the Premises or any part thereof, or enter into any license or concession agreements or otherwise permit the occupancy or use of the Premises or
any part thereof by any persons other than Tenant and its employees and contractors (all of the foregoing are hereinafter sometimes referred to collectively as “Transfers” and any person to whom any Transfer is made or sought to be
made is hereinafter sometimes referred to as a “Transferee”). If Tenant desires Landlord’s consent to any Transfer, Tenant shall notify Landlord in writing, which notice (the “Transfer Notice”) shall include
(i) the proposed effective date of the Transfer, which shall not be less than thirty (30) days nor more than one hundred eighty (180) days after the date of delivery of the Transfer Notice, (ii) a description of the portion of
the Premises to be transferred (the “Subject Space”), (iii) all of the terms of the proposed Transfer and the consideration therefor, including calculation of the “Transfer Premium”, as that term is defined in
Section 14.3 below, in connection with such Transfer, the name and address of the proposed Transferee, and a copy of all existing executed and/or proposed documentation pertaining to the proposed Transfer, and
(iv) current financial statements of the proposed Transferee certified by an officer, partner or owner thereof, business credit and personal references and history of the proposed Transferee and any other information reasonably required by
Landlord which will enable Landlord to determine the financial responsibility, character, and reputation of the proposed Transferee, nature of such Transferee’s business and proposed use of the Subject Space. Any Transfer made without
Landlord’s prior written consent shall, at Landlord’s option, be null, void and of no effect, and shall, at Landlord’s option, constitute a default by Tenant under this Lease. Whether or not Landlord consents to any proposed Transfer,
Tenant shall pay Landlord’s reasonable review and processing fees, as well as any reasonable professional fees (including, without limitation, attorneys’, accountants’, architects’, engineers’ and consultants’ fees)
incurred by Landlord, within thirty (30) days after written request by Landlord, provided that such fees shall not exceed Two Thousand Five Hundred Dollars ($2,500.00) for any such Transfer in the ordinary course of business. For purposes of
this Lease, “in the ordinary course of business” shall include, without limitation, the review of documents on no more than three (3) occasions in connection with any particular Transfer. 

  

					
		  	-26-	  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

 14.2 Landlord’s Consent. Landlord shall not unreasonably withhold,
condition or delay its consent to any proposed Transfer of the Subject Space to the Transferee on the terms specified in the Transfer Notice, and shall grant or withhold its consent within thirty (30) days following Landlord’s receipt of a
complete Transfer Notice. If Landlord fails to respond within such thirty (30) day period, then Tenant may send Landlord a reminder notice setting forth such failure containing the following sentence at the top of such notice in bold,
capitalized font at least twelve (12) points in size: “LANDLORD’S FAILURE TO RESPOND TO THIS NOTICE WITHIN FIVE (5) BUSINESS DAYS SHALL RESULT IN LANDLORD’S DEEMED APPROVAL OF TENANT’S REQUEST FOR
TRANSFER” (the “Transfer Reminder Notice”). Any such Transfer Reminder Notice shall include a complete copy of Tenant’s Transfer Notice. If Landlord fails to respond within five (5) business days after receipt of
a Transfer Reminder Notice, then Tenant’s Transfer for which Tenant requested Landlord’s approval shall be deemed approved by Landlord. Without limitation as to other reasonable grounds for withholding consent, the parties hereby agree
that it shall be reasonable under this Lease and under any applicable law for Landlord to withhold consent to any proposed Transfer where one or more of the following apply: 

14.2.1 The Transferee is, in Landlord’s commercially reasonable business judgment, of a character or reputation or engaged in a business
which is not consistent with the quality of the Building or the Project; 
 14.2.2 The Transferee is either a governmental agency or
instrumentality thereof; 
 14.2.3 The Transferee is not a party of reasonable financial worth and/or financial stability in light of the
responsibilities to be undertaken in connection with the Transfer on the date consent is requested; or 
 14.2.4 The proposed Transfer would
cause a violation of another lease for space in the Project, or would give an occupant of the Project a right to cancel its lease. 
 If
Landlord consents to any Transfer pursuant to the terms of this Section 14.2 (and does not exercise any recapture rights Landlord may have under Section 14.4 of this Lease), Tenant may within six
(6) months after Landlord’s consent, but not later than the expiration of said six-month period, enter into such Transfer of the Premises or portion thereof, upon substantially the same terms and
conditions as are set forth in the Transfer Notice furnished by Tenant to Landlord pursuant to Section 14.1 of this Lease, provided that if there are any changes in the terms and conditions from those specified in the
Transfer Notice such that Landlord would initially have been entitled to refuse its consent to such Transfer under this Section 14.2, Tenant shall again submit the Transfer to Landlord for its approval and other action
under this Article 14 (including Landlord’s right of recapture, if any, under Section 14.4 of this Lease). Notwithstanding anything to the contrary in this Lease, if Tenant or any proposed Transferee claims that
Landlord has unreasonably withheld or delayed its consent under Section 14.2 or otherwise has breached or acted unreasonably under this Article 14, their sole remedies shall be a suit for contract damages (other than
damages for injury to, or interference with, Tenant’s business including, without limitation, loss of profits, however occurring) (subject to Section 29.13 below) or declaratory judgment and an injunction for the
relief sought, and Tenant hereby waives all other remedies, including, without limitation, any right at law or equity to terminate this Lease, on its own behalf and, to the extent permitted under all applicable laws, on behalf of the proposed
Transferee. 
 14.3 Transfer Premium. If Landlord consents to a Transfer, as a condition thereto which the parties hereby agree
is reasonable, Tenant shall pay to Landlord fifty percent (50%) of any “Transfer Premium,” as that term is defined in this Section 14.3, received by Tenant from such Transferee. “Transfer Premium” shall mean
all rent, additional rent or other consideration payable by such Transferee in connection with the Transfer in excess of the Rent and Additional Rent payable by Tenant under this Lease during the term of the Transfer on a per rentable square foot
basis if less than all of the Premises is transferred, and after deduction of (i) any costs of improvements or alterations made to the Subject Space in connection with such Transfer, (ii) any free base rent or other reasonable economic
considerations reasonably provided to the Transferee, (iii) brokerage commissions and marketing expenses paid in connection with such Transfer, (iv) reasonable legal fees incurred in connection with such Transfer, and (v) any amounts
payable to Landlord under Section 14.1 above. “Transfer Premium” shall also include, but not be limited to, key money, bonus money or other cash consideration paid by Transferee to Tenant in connection with
such Transfer, and any payment in excess of fair market value for services rendered by Tenant to Transferee or for assets, fixtures, inventory, equipment, or furniture transferred by Tenant to Transferee in connection with such Transfer. The
determination of the amount of Landlord’s applicable share of the Transfer Premium shall be made on a monthly basis 

  

					
		  	-27-	  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

 
as rent or other consideration is received by Tenant under the Transfer. No Transfer Premium shall be payable in connection with any Permitted Transfer. 

14.4 Landlord’s Option as to Subject Space. Notwithstanding anything to the contrary contained in this Article 14, in
the event Tenant contemplates a Transfer which, together with all prior Transfers then remaining in effect, would cause fifty percent (50%) or more of the Premises to be Transferred for more than twenty five percent (25%) of the then remaining
Lease Term (taking into account any extension of the Lease Term which has irrevocably exercised by Tenant), Tenant shall give Landlord notice (the “Intention to Transfer Notice”) of such contemplated Transfer (whether or not the
contemplated Transferee or the terms of such contemplated Transfer have been determined). The Intention to Transfer Notice shall specify the portion of and amount of rentable square feet of the Premises which Tenant intends to Transfer (the
“Contemplated Transfer Space”), the contemplated date of commencement of the Contemplated Transfer (the “Contemplated Effective Date”), and the contemplated length of the term of such contemplated Transfer, and
shall specify that such Intention to Transfer Notice is delivered to Landlord pursuant to this Section 14.4 in order to allow Landlord to elect to recapture the Contemplated Transfer Space. Thereafter, Landlord shall have
the option, by giving written notice to Tenant within thirty (30) days after receipt of any Intention to Transfer Notice, to recapture the Contemplated Transfer Space. Such recapture shall cancel and terminate this Lease with respect to such
Contemplated Transfer Space as of the Contemplated Effective Date. In the event of a recapture by Landlord, if this Lease shall be canceled with respect to less than the entire Premises, the Rent reserved herein shall be prorated on the basis of the
number of rentable square feet retained by Tenant in proportion to the number of rentable square feet contained in the Premises, and this Lease as so amended shall continue thereafter in full force and effect, and upon request of either party, the
parties shall execute written confirmation of the same. If Landlord declines, or fails to elect in a timely manner, to recapture such Contemplated Transfer Space under this Section 14.4, then, subject to the other terms of
this Article 14, for a period of nine (9) months (the “Nine Month Period”) commencing on the last day of such thirty (30) day period, Landlord shall not have any right to recapture the Contemplated Transfer Space
with respect to any Transfer made during the Nine Month Period, provided that any such Transfer is substantially on the terms set forth in the Intention to Transfer Notice, and provided further that any such Transfer shall be subject to the
remaining terms of this Article 14. If such a Transfer is not so consummated within the Nine Month Period (or if a Transfer is so consummated, then upon the expiration of the term of any Transfer of such Contemplated Transfer Space
consummated within such Nine Month Period), Tenant shall again be required to submit a new Intention to Transfer Notice to Landlord with respect any contemplated Transfer, as provided above in this Section 14.4.
Notwithstanding anything to the contrary contained in this Section 14.4, Landlord’s right of recapture shall not apply to a subletting of all or a portion of the Premises to COI Pharmaceuticals, Inc., a Delaware
corporation. 
 14.5 Effect of Transfer. If Landlord consents to a Transfer, (i) the terms and conditions of this Lease
shall in no way be deemed to have been waived or modified, (ii) such consent shall not be deemed consent to any further Transfer by either Tenant or a Transferee, (iii) Tenant shall deliver to Landlord, promptly after execution, an
original executed copy of all documentation pertaining to the Transfer in form reasonably acceptable to Landlord, (iv) Tenant shall furnish upon Landlord’s request a complete statement, certified by an independent certified public
accountant, or Tenant’s chief financial officer, setting forth in detail the computation of any Transfer Premium Tenant has derived and shall derive from such Transfer, and (v) no Transfer relating to this Lease or agreement entered into
with respect thereto, whether with or without Landlord’s consent, shall relieve Tenant or any guarantor of the Lease from any liability under this Lease, including, without limitation, in connection with the Subject Space. Landlord or its
authorized representatives shall have the right at all reasonable times, at Tenant’s local offices, to audit the books, records and papers of Tenant relating to any Transfer, and shall have the right to make copies thereof (provided that Tenant
shall have no obligation to make copies thereof). If the Transfer Premium respecting any Transfer shall be found understated, Tenant shall, within thirty (30) days after demand, pay the deficiency, and if understated by more than two percent
(2%), Tenant shall pay Landlord’s costs of such audit. 
 14.6 Additional Transfers. For purposes of this Lease, subject
to Section 14.8 below, the term “Transfer” shall also include (i) if Tenant is a partnership, the withdrawal or change, voluntary, involuntary or by operation of law, of fifty percent (50%) or more of
the partners, or transfer of fifty percent (50%) or more of partnership interests, within a twelve (12)-month period, or the dissolution of the partnership without immediate reconstitution thereof, and (ii) if Tenant is a closely held
corporation (i.e., whose stock is not publicly held and not traded through an exchange or over the counter), (A) the dissolution, merger, consolidation or other reorganization of Tenant or (B)

  

					
		  	-28-	  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

 
the sale or other transfer of an aggregate of fifty percent (50%) or more of the voting shares of Tenant (other than to immediate family members by reason of gift or death), within a twelve
(12)-month period, or (C) the sale, mortgage, hypothecation or pledge of an aggregate of fifty percent (50%) or more of the value of the unencumbered assets of Tenant within a twelve (12)-month period. 

14.7 Occurrence of Default. Any Transfer hereunder shall be subordinate and subject to the provisions of this Lease, and if this
Lease shall be terminated during the term of any Transfer, Landlord shall have the right to: (i) treat such Transfer as cancelled and repossess the Subject Space by any lawful means, or (ii) require that such Transferee attorn to and
recognize Landlord as its landlord under any such Transfer. If an Event of Default has occurred and is continuing, Landlord is hereby irrevocably authorized, as Tenant’s agent and
attorney-in-fact, to direct any Transferee to make all payments under or in connection with the Transfer directly to Landlord (which Landlord shall apply towards
Tenant’s obligations under this Lease) until such default is cured. Such Transferee shall rely on any representation by Landlord that Tenant is in default hereunder, without any need for confirmation thereof by Tenant. Upon any assignment, the
assignee shall assume in writing all obligations and covenants of Tenant thereafter to be performed or observed under this Lease. No collection or acceptance of rent by Landlord from any Transferee shall be deemed a waiver of any provision of this
Article 14 or the approval of any Transferee or a release of Tenant from any obligation under this Lease, whether theretofore or thereafter accruing. In no event shall Landlord’s enforcement of any provision of this Lease against any
Transferee be deemed a waiver of Landlord’s right to enforce any term of this Lease against Tenant or any other person. If Tenant’s obligations hereunder have been guaranteed, Landlord’s consent to any Transfer shall not be effective
unless the guarantor also consents to such Transfer. 
 14.8 Deemed Consent Transfers; Permitted Transferees. Notwithstanding
anything to the contrary contained in this Lease, (A) an assignment or subletting of all or a portion of the Premises to an Affiliate of Tenant (an “Affiliate” shall mean an entity which is controlled by, controls, or is under
common control with, Tenant, but only so long as such transferee remains an Affiliate of Tenant), (B) a sale of corporate shares of capital stock in Tenant in connection with any public offering or sale of stock on a nationally-recognized stock
exchange, (C) the sale, assignment, transfer or hypothecation of any stock or other ownership interest in Tenant in connection with any bona fide financing or capitalization for the benefit of Tenant, (D) the sale, assignment, transfer or
hypothecation of any stock or other ownership interest in Tenant to an existing shareholder of Tenant (i.e., an existing shareholder in Tenant as of the full execution and delivery of this Lease), (E) an assignment of the Lease to an entity which
acquires all or substantially all of the stock or assets of Tenant in one or a series of transactions, or (F) an assignment of the Lease to an entity which is the resulting entity of a merger or consolidation of Tenant during the Lease Term,
shall not be deemed a Transfer requiring Landlord’s consent under this Article 14, (any such assignee or subtenant described in items (A) through (F) of this Section 14.8 is referred to as a
“Permitted Transferee” and each such transfer as a “Permitted Transfer”) provided that (i) Tenant notifies Landlord at least fifteen (15) days prior to the effective date of any such assignment or sublease
(unless such prior notice is prohibited by applicable law, in which case Tenant shall give notice as soon as permitted) and promptly supplies Landlord with any documents or information reasonably requested by Landlord regarding such Transfer or
Permitted Transferee as set forth above, (ii) Tenant delivers evidence of insurance as required under this Lease with respect to the Permitted Transferee, (iii) an Event of Default has not occurred and is continuing, and such assignment or
sublease is not a subterfuge by Tenant to avoid its obligations under this Lease, (iv) such Permitted Transferee shall be of a character and reputation consistent with the quality of the Building, (v) no assignment or sublease relating to
this Lease, whether with or without Landlord’s consent, shall relieve Tenant from any liability under this Lease, (vi) the liability of such Permitted Transferee under an assignment shall be joint and several with Tenant, and
(vii) the tangible net worth of such Permitted Transferee, as determined in accordance with generally accepted accounting principles, is not less than the greater of (1) the tangible net worth of Tenant on the date of this Lease, and
(2) the tangible net worth of Tenant immediately prior to the occurrence of such assignment or sublease. The occurrence of a Transfer pursuant to this Section 14.8 shall not waive Landlord’s rights as to any
subsequent Transfers. The right to Transfer to an Affiliate pursuant to Section 14.8(A) shall be subject to the condition that such Permitted Transferee remains an Affiliate of Tenant and if such Permitted Transferee ceases
to be an Affiliate of Tenant, it shall so notify Landlord in writing within ten (10) business days after such event and, upon the written request of Landlord, transfer, assign, set over and/or re-assign
this Lease and its interest in the Premises, as applicable, to Tenant or, subject to complying with this condition, another Affiliate of Tenant. An assignee of Tenant’s entire interest in this Lease who qualifies as a Permitted Transferee
may also be referred to herein as a “Permitted Transferee Assignee.” “Control”, as used in this Section 14.8, shall mean the ownership, directly

  

					
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[Synthorx Inc.]

 
or indirectly, of more than fifty percent (50%) of the voting securities of, or possession of the right to vote, in the ordinary direction of its affairs, of more than fifty percent (50%) of the
voting interest in, any person or entity. 
 15. SURRENDER OF PREMISES; OWNERSHIP AND REMOVAL OF TRADE FIXTURES 

15.1 Surrender of Premises. No act or thing done by Landlord or any agent or employee of Landlord during the Lease Term shall be
deemed to constitute an acceptance by Landlord of a surrender of the Premises unless such intent is specifically acknowledged in writing by Landlord. The delivery of keys to the Premises to Landlord or any agent or employee of Landlord shall not
constitute a surrender of the Premises or effect a termination of this Lease, whether or not the keys are thereafter retained by Landlord, and notwithstanding such delivery Tenant shall be entitled to the return of such keys at any reasonable time
upon request until this Lease shall have been properly terminated. The voluntary or other surrender of this Lease by Tenant, whether accepted by Landlord or not, or a mutual termination hereof, shall not work a merger, and at the option of Landlord
shall operate as an assignment to Landlord of all subleases or subtenancies affecting the Premises or terminate any or all such sublessees or subtenancies. 

15.2 Removal of Tenant Property by Tenant. Upon the expiration of the Lease Term, or upon any earlier termination of this Lease,
Tenant shall, subject to the provisions of this Article 15, quit and surrender possession of the Premises to Landlord in as good order and condition as when Tenant took possession and as thereafter improved by Landlord and/or Tenant,
reasonable wear and tear and repairs which are specifically made the responsibility of Landlord hereunder excepted. Upon such expiration or termination, Tenant shall, without expense to Landlord, remove or cause to be removed from the Premises all
debris and rubbish, and such items of furniture, equipment, free-standing cabinet work, movable partitions and other articles of personal property owned by Tenant or installed or placed by Tenant at its expense in the Premises, and such similar
articles of any other persons claiming under Tenant, as Landlord may, in its sole discretion, require to be removed (provided that Tenant, in its sole discretion, may remove all of Tenant’s personal property, at any time prior to the expiration
of the Lease Term or any earlier termination of this Lease, regardless of any such election by Landlord), and Tenant shall repair at its own expense all damage to the Premises and Building resulting from such removal. 

15.3 Environmental Assessment. In connection with its surrender of the Premises, Tenant shall submit to Landlord, at least one
hundred twenty (120) days prior to the expiration date of this Lease (or in the event of an earlier termination of this Lease, as soon as reasonably possible following such termination), an environmental Assessment of the Premises by a
competent and experienced environmental engineer or engineering firm reasonably satisfactory to Landlord (pursuant to a contract reasonably approved by Landlord and providing that Landlord can rely on the Environmental Assessment), which
(i) evidences that the Premises are in a clean and safe condition and free and clear of any Hazardous Materials for which Tenant has responsibility under this Lease; and (ii) includes a review of the Premises by an environmental consultant
for asbestos, mold, fungus, spores, and other moisture conditions, on-site chemical use, and lead-based paint. If such Environmental Assessment reveals that remediation or
Clean-up is required under any Environmental Laws in connection with any Hazardous Materials for which Tenant has responsibility under this Lease, Tenant shall submit a remediation plan prepared by a
recognized environmental consultant and shall be responsible for all costs of remediation and Clean-up, as more particularly provided in Section 5.3, above. 

15.4 Condition of the Building and Premises Upon Surrender. In addition to the above requirements of this
Article 15, upon the expiration of the Lease Term, or upon any earlier termination of this Lease, Tenant shall, surrender the Premises and Building such that the same are in compliance with all of Tenant’s obligations
under this Lease, including those relating to improvement, repair, maintenance, compliance with law, testing and other related obligations of Tenant set forth in Article 7 of this Lease. In the event that the Premises shall
be surrendered in a condition which does not comply with the terms of this Section 15.4, because Tenant failed to comply with its obligations set forth in Lease, then following thirty (30) days’ notice to Tenant,
during which thirty (30) day period Tenant shall have the right to cure such noncompliance, Landlord shall be entitled to expend all reasonable costs in order to cause the same to comply with the required condition upon surrender and Tenant
shall immediately reimburse Landlord for all such costs upon notice and Tenant shall be deemed during the period that Tenant or Landlord, as the case may be, perform obligations relating to the Surrender Improvements to be in holdover under
Article 16 of this Lease. 

  

					
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[Synthorx Inc.]

 16. HOLDING OVER If Tenant holds over after the expiration of the Lease Term or earlier
termination thereof, with the express or implied consent of Landlord, such tenancy shall be from month-to-month only, and shall not constitute a renewal hereof or an
extension for any further term. If Tenant holds over after the expiration of the Lease Term of earlier termination thereof, without the express or implied consent of Landlord, such tenancy shall be deemed to be a tenancy by sufferance only, and
shall not constitute a renewal hereof or an extension for any further term. In either case, Base Rent shall be payable at a monthly rate equal to: (i) for the first month of such holdover, one hundred twenty-five percent (125%) of the Base Rent
applicable during the last rental period of the Lease Term under this Lease, and (ii) for each month thereafter, one hundred fifty percent (150%) of the Base Rent applicable during the last rental period of the Lease Term under this Lease. Such
month-to-month tenancy or tenancy by sufferance, as the case may be, shall be subject to every other applicable term, covenant and agreement contained herein. Nothing
contained in this Article 16 shall be construed as consent by Landlord to any holding over by Tenant, and Landlord expressly reserves the right to require Tenant to surrender possession of the Premises to Landlord as provided in this Lease upon the
expiration or other termination of this Lease. The provisions of this Article 16 shall not be deemed to limit or constitute a waiver of any other rights or remedies of Landlord provided herein or at law. If Tenant fails to surrender the Premises
upon the termination or expiration of this Lease, in addition to any other liabilities to Landlord accruing therefrom, Tenant shall protect, defend, indemnify and hold Landlord harmless from all loss, costs (including reasonable attorneys’
fees) and liability resulting from such failure, including, without limiting the generality of the foregoing, any claims made by any succeeding tenant founded upon such failure to surrender and any lost profits to Landlord resulting therefrom;
provided, however, that if such holding over is with the express or implied consent of Landlord, in no event shall Tenant be liable for consequential damages attributable to the first thirty (30) days of such holding over by Tenant. In the
event of any potential or actual holding over of the Premises by Tenant, Tenant may elect to send one or more written notices to Landlord (specifically referencing this Article 16) requesting an update as to whether Landlord has entered into
a third-party lease for the Premises following the expiration or earlier termination of this Lease, and Landlord shall, within ten (10) business days of its receipt of such notice from Tenant, notify Tenant (i) whether or not Landlord has
entered into a third-party lease as of the date of such notice for the Premises following the expiration or earlier termination of this Lease, and (ii) the date upon which Landlord requires Tenant to surrender the Premises in order for Landlord
to timely deliver the Premises to the tenant under such third-party lease and avoid any claims by such tenant founded upon such failure by Tenant to timely surrender the Premises and any lost profits to Landlord resulting therefrom; provided,
however, in no event shall any such notice by Tenant to Landlord, or any subsequent notice from Landlord to Tenant (or any failure by Landlord to provide such notice) be deemed a waiver of any of Tenant’s obligations or liabilities under this
Article 16. 
 17. ESTOPPEL CERTIFICATES Within ten (10) business days following a request in writing by Landlord, Tenant shall
execute, acknowledge and deliver to Landlord an estoppel certificate, which, as submitted by Landlord, shall be substantially in the form of Exhibit D, attached hereto (or such other form as may be required by any prospective
mortgagee or purchaser of the Project, or any portion thereof, provided that nothing in any estoppel certificate shall amend the terms and conditions of this Lease), indicating therein any exceptions thereto that may exist at that time, and shall
also contain any other information reasonably requested by Landlord or Landlord’s mortgagee or prospective mortgagee. Any such certificate may be relied upon by any prospective mortgagee or purchaser of all or any portion of the Project. Tenant
shall execute and deliver whatever other instruments may be reasonably required for such purposes. At any time during the Lease Term (but not more than twice in any twelve (12) month period, except in connection with a sale or refinance of the
Project, if Tenant is in monetary or material non-monetary default under this Lease, or if Tenant has identified a proposed Transferee under Article 14 above), Landlord may require Tenant to provide
Landlord with a current financial statement and financial statements of the two (2) years prior to the current financial statement year. Such statements shall be prepared in accordance with generally accepted accounting principles and, if such
is the normal practice of Tenant, shall be audited by an independent certified public accountant. Failure of Tenant to timely execute, acknowledge and deliver such estoppel certificate or other instruments shall constitute an acceptance of the
Premises and an acknowledgment by Tenant that statements included in the estoppel certificate are true and correct, without exception. 
 18.
SUBORDINATION This Lease shall be subject and subordinate to all present and future ground or underlying leases of the Building or Project and to the lien of any mortgage, trust deed or other encumbrances now or hereafter in force
against the Building or Project or any part thereof, if any, and to all renewals, extensions, modifications, consolidations and replacements thereof, and to all advances made or hereafter to be made upon the security of such mortgages or trust
deeds, unless the holders of such mortgages, trust deeds or other 

  

					
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[Synthorx Inc.]

 
encumbrances, or the lessors under such ground lease or underlying leases, require in writing that this Lease be superior thereto. Tenant covenants and agrees in the event any proceedings are
brought for the foreclosure of any such mortgage or deed in lieu thereof (or if any ground lease is terminated), to attorn, without any deductions or set-offs whatsoever, to the lienholder or purchaser or any
successors thereto upon any such foreclosure sale or deed in lieu thereof (or to the ground lessor), if so requested to do so by such purchaser or lienholder or ground lessor, and to recognize such purchaser or lienholder or ground lessor as the
lessor under this Lease, provided such lienholder or purchaser or ground lessor shall agree to accept this Lease and not disturb Tenant’s occupancy, so long as Tenant timely pays the rent and observes and performs the terms, covenants and
conditions of this Lease to be observed and performed by Tenant. Landlord’s interest herein may be assigned as security at any time to any lienholder. Tenant shall, within ten (10) business days of request by Landlord, execute such further
commercially reasonable instruments or assurances as Landlord may reasonably deem necessary to evidence or confirm the subordination or superiority of this Lease to any such mortgages, trust deeds, ground leases or underlying leases. Tenant waives
the provisions of any current or future statute, rule or law which may give or purport to give Tenant any right or election to terminate or otherwise adversely affect this Lease and the obligations of the Tenant hereunder in the event of any
foreclosure proceeding or sale. 
 19. DEFAULTS; REMEDIES 

19.1 Events of Default. The occurrence of any of the following shall constitute a default of this Lease by Tenant (each, an
“Event of Default”): 
 19.1.1 Any failure by Tenant to pay any Rent or any other charge required to be paid under this
Lease, or any part thereof, when due unless such failure is cured within five (5) business days after notice from Landlord to Tenant; or 

19.1.2 Except for events described in Sections 19.1.1, 19.1.3 and 19.1.4, any failure by Tenant to observe or perform
any other provision, covenant or condition of this Lease to be observed or performed by Tenant where such failure continues for thirty (30) days after written notice thereof from Landlord to Tenant; provided that if the nature of such default
is such that the same cannot reasonably be cured within a thirty (30) day period, Tenant shall not be deemed to be in default if it diligently commences such cure within such period and thereafter diligently proceeds to rectify and cure such
default; or 
 19.1.3 Abandonment of all or a substantial portion of the Premises by Tenant; or 

19.1.4 The failure by Tenant to observe or perform according to the provisions of Articles 5, 14, 17 or 18 of this
Lease where such failure continues for more than three (3) business days after notice from Landlord. 
 The notice periods provided
herein are in lieu of, and not in addition to, any notice periods provided by law. 
 19.2 Remedies Upon Default. Upon the
occurrence of any Event of Default by Tenant, Landlord shall have, in addition to any other remedies available to Landlord at law or in equity (all of which remedies shall be distinct, separate and cumulative), the option to pursue any one or more
of the following remedies, each and all of which shall be cumulative and nonexclusive, without any notice or demand whatsoever. 
 19.2.1
Terminate this Lease, in which event Tenant shall, upon written notice, immediately surrender the Premises to Landlord, and if Tenant fails to do so, Landlord may, without prejudice to any other remedy which it may have for possession or arrearages
in rent, enter upon and take possession of the Premises and expel or remove Tenant and any other person who may be occupying the Premises or any part thereof, without being liable for prosecution or any claim or damages therefor; and Landlord may
recover from Tenant the following: 
 (i) The worth at the time of award of the unpaid rent which has been earned at the time
of such termination; plus 

  

					
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[Synthorx Inc.]

 (ii) The worth at the time of award of the amount by which the unpaid rent
which would have been earned after termination until the time of award exceeds the amount of such rental loss that Tenant proves could have been reasonably avoided; plus 

(iii) The worth at the time of award of the amount by which the unpaid rent for the balance of the Lease Term after the time of
award exceeds the amount of such rental loss that Tenant proves could have been reasonably avoided; plus 
 (iv) Any other
amount necessary to compensate Landlord for all the detriment proximately caused by Tenant’s failure to perform its obligations under this Lease or which in the ordinary course of things would be likely to result therefrom, specifically
including but not limited to, brokerage commissions and advertising expenses incurred, expenses of remodeling the Premises or any portion thereof for a new tenant, whether for the same or a different use, and any special concessions made to obtain a
new tenant; and 
 (v) At Landlord’s election, such other amounts in addition to or in lieu of the foregoing as may be
permitted from time to time by applicable law. 
 The term “rent” as used in this Section 19.2
shall be deemed to be and to mean all sums of every nature required to be paid by Tenant pursuant to the terms of this Lease, whether to Landlord or to others. As used in Sections 19.2.1(i) and (ii), above, the “worth at the time
of award” shall be computed by allowing interest at the rate set forth in Article 25 of this Lease, but in no case greater than the maximum amount of such interest permitted by law. As used in
Section 19.2.1(iii) above, the “worth at the time of award” shall be computed by discounting such amount at the discount rate of the Federal Reserve Bank of San Francisco at the time of award plus one
percent (1%). 
 19.2.2 Landlord shall have the remedy described in California Civil Code Section 1951.4 (lessor may continue lease in
effect after lessee’s breach and abandonment and recover rent as it becomes due, if lessee has the right to sublet or assign, subject only to reasonable limitations). Accordingly, if Landlord does not elect to terminate this Lease on account of
any Event of Default by Tenant, Landlord may, from time to time, without terminating this Lease, enforce all of its rights and remedies under this Lease, including the right to recover all rent as it becomes due. 

19.2.3 Landlord shall at all times have the rights and remedies (which shall be cumulative with each other and cumulative and in addition to
those rights and remedies available under Sections 19.2.1 and 19.2.2, above, or any law or other provision of this Lease), without prior demand or notice except as required by applicable law, to seek any declaratory, injunctive or
other equitable relief, and specifically enforce this Lease, or restrain or enjoin a violation or breach of any provision hereof. 
 19.3
Subleases of Tenant. Whether or not Landlord elects to terminate this Lease on account of any Event of Default by Tenant, as set forth in this Article 19, Landlord shall have the right to terminate any and all subleases,
licenses, concessions or other consensual arrangements for possession entered into by Tenant and affecting the Premises or may, in Landlord’s sole discretion, succeed to Tenant’s interest in such subleases, licenses, concessions or
arrangements. In the event of Landlord’s election to succeed to Tenant’s interest in any such subleases, licenses, concessions or arrangements, Tenant shall, as of the date of notice by Landlord of such election, have no further right to
or interest in the rent or other consideration receivable thereunder. 
 19.4 Efforts to Relet. No re-entry or repossession, repairs, maintenance, changes, alterations and additions, reletting, appointment of a receiver to protect Landlord’s interests hereunder, or any other action or omission by Landlord
shall be construed as an election by Landlord to terminate this Lease or Tenant’s right to possession, or to accept a surrender of the Premises, nor shall same operate to release Tenant in whole or in part from any of Tenant’s obligations
hereunder, unless express written notice of such intention is sent by Landlord to Tenant. Tenant hereby irrevocably waives any right otherwise available under any law to redeem or reinstate this Lease. 

  

					
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[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

 19.5 Landlord Default. 

19.5.1 General. Notwithstanding anything to the contrary set forth in this Lease, Landlord shall not be in default in the
performance of any obligation required to be performed by Landlord pursuant to this Lease unless Landlord fails to perform such obligation within thirty (30) days after the receipt of notice from Tenant specifying in detail Landlord’s
failure to perform; provided, however, if the nature of Landlord’s obligation is such that more than thirty (30) days are required for its performance, then Landlord shall not be in default under this Lease if it shall commence such
performance within such thirty (30) day period and thereafter diligently pursue the same to completion. Upon any such default by Landlord under this Lease, Tenant may, except as otherwise specifically provided in this Lease to the contrary,
exercise any of its rights provided at law or in equity. 
 19.5.2 Abatement of Rent. In the event that Tenant is prevented
from using, and does not use, the Premises or any portion thereof, as a result of (i) any repair, maintenance or alteration performed by Landlord, or which Landlord failed to perform, after the Lease Commencement Date and required by this
Lease, which substantially interferes with Tenant’s use of the Premises, or (ii) any failure by Landlord to provide services, utilities or access to the Premises required by this Lease to be provided by Landlord (either such set of
circumstances as set forth in items (i) or (ii), above, to be known as an “Abatement Event”), then Tenant shall give Landlord notice of such Abatement Event, and if such Abatement Event continues for five (5) consecutive
business days after Landlord’s receipt of any such notice (the “Eligibility Period”), then the Base Rent and Tenant’s Share of Direct Expenses shall be abated or reduced, as the case may be, after expiration of the
Eligibility Period for such time that Tenant continues to be so prevented from using, and does not use for the normal conduct of Tenant’s business, the Premises or a portion thereof, in the proportion that the rentable area of the portion of
the Premises that Tenant is prevented from using, and does not use, bears to the total rentable area of the Premises; provided, however, in the event that Tenant is prevented from using, and does not use, a portion of the Premises for a period of
time in excess of the Eligibility Period and the remaining portion of the Premises is not sufficient to allow Tenant to effectively conduct its business therein, and if Tenant does not conduct its business from such remaining portion, then for such
time after expiration of the Eligibility Period during which Tenant is so prevented from effectively conducting its business therein, the Base Rent and Tenant’s Share of Direct Expenses for the entire Premises shall be abated for such time as
Tenant continues to be so prevented from using, and does not use, the Premises. Tenant shall not have a right to receive an abatement of Rent if Tenant is otherwise entitled to receive proceeds from business interruption insurance that Tenant is
obligated to carry pursuant to Section 10.3.3 above. If, however, Tenant reoccupies any portion of the Premises during such period, the Rent allocable to such reoccupied portion, based on the proportion that the rentable
area of such reoccupied portion of the Premises bears to the total rentable area of the Premises, shall be payable by Tenant from the date Tenant reoccupies such portion of the Premises. To the extent an Abatement Event is caused by an event covered
by Articles 11 or 13 of this Lease, then Tenant’s right to abate rent shall be governed by the terms of such Article 11 or 13, as applicable, and the Eligibility Period shall not be applicable thereto.
Such right to abate Base Rent and Tenant’s Share of Direct Expenses shall be Tenant’s sole and exclusive remedy for rent abatement at law or in equity for an Abatement Event. Except as provided in this
Section 19.5.2, nothing contained herein shall be interpreted to mean that Tenant is excused from paying Rent due hereunder. 

20. COVENANT OF QUIET ENJOYMENT Landlord covenants that Tenant, on paying the Rent, charges for services and other payments herein reserved and on
keeping, observing and performing all the other terms, covenants, conditions, provisions and agreements herein contained on the part of Tenant to be kept, observed and performed, shall, during the Lease Term, peaceably and quietly have, hold and
enjoy the Premises subject to the terms, covenants, conditions, provisions and agreements hereof without interference by any persons lawfully claiming by or through Landlord. The foregoing covenant is in lieu of any other covenant express or
implied. 
 21. SECURITY DEPOSIT Concurrently with Tenant’s execution of this Lease, Tenant shall deposit with Landlord a security deposit (the
“Security Deposit”) in the amount set forth in Section 8 of the Summary, as security for the faithful performance by Tenant of all of its obligations under this Lease. Upon an Event of Default by Tenant defaults with respect to
any provisions of this Lease, including, but not limited to, the provisions relating to the payment of Rent, the removal of property and the repair of resultant damage, Landlord may, without notice to Tenant, but shall not be required to apply all
or any part of the Security Deposit for the payment of any Rent or any other sum in default and Tenant shall, within five (5) business days of demand therefor, restore the Security Deposit to its original amount. Any unapplied portion of the
Security Deposit shall be returned to Tenant, or, at Landlord’s 

  

					
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[Synthorx Inc.]

 
option, to the last assignee of Tenant’s interest hereunder, within sixty (60) days following the expiration of the Lease Term. Tenant shall not be entitled to any interest on the
Security Deposit. Tenant hereby irrevocably waives and relinquishes any and all rights, benefits, or protections, if any, Tenant now has, or in the future may have, under Section 1950.7 of the California Civil Code, any successor statute, and
all other provisions of law, now or hereafter in effect, including, but not limited to, any provision of law which (i) establishes the time frame by which a landlord must refund a security deposit under a lease, and/or (ii) provides that a
landlord may claim from a security deposit only those sums reasonably necessary to remedy defaults in the payment of rent, to repair damage caused by a tenant or to clean the subject premises. Tenant acknowledges and agrees that (a) any
statutory time frames for the return of a security deposit are superseded by the express period identified in this Article 21, above, and (b) rather than be so limited, Landlord may claim from the Security Deposit (1) any and all sums
expressly identified in this Article 21, above, and (2) any additional sums reasonably necessary to compensate Landlord for any and all losses or damages caused by Tenant’s default of this Lease, including, but not limited to, all damages
or rent due upon termination of Lease pursuant to Section 1951.2 of the California Civil Code. 
 22. COMMUNICATIONS AND COMPUTER LINE Tenant may
install, maintain, replace, remove or use any communications or computer wires and cables serving the Premises (collectively, the “Lines”), provided that Tenant shall obtain Landlord’s prior written consent (which shall not be
unreasonably withheld, conditioned or delayed), use an experienced and qualified contractor approved in writing by Landlord, and comply with all of the other provisions of Articles 7 and 8 of this Lease. Tenant shall pay all costs in connection
therewith. Tenant shall, at Tenant’s sole cost and expense, remove any Lines located in or serving the Premises prior to the expiration or earlier termination of this Lease. 

23. SIGNS Landlord, at its initial cost and expense, shall install (i) Building standard suite entry signage, and (ii) an entry in the
Building directory located in the lobby. Any changes to Tenant’s suite entry signage, or lobby directory signage shall be subject to Landlord’s prior written approval (which shall not be unreasonably withheld, conditioned or delayed) and
shall be performed at Tenant’s sole cost and expense. 
 24. COMPLIANCE WITH LAW 

24.1 Tenant’s Compliance with Law Obligations. Tenant shall not do anything or suffer anything to be done in or about the
Premises or the Project which will in any way conflict with any law, statute, ordinance or other governmental rule, regulation or requirement now in force or which may hereafter be enacted or promulgated. At its sole cost and expense, Tenant shall
promptly comply with all such governmental measures that relate to (i) Tenant’s use or occupancy of the Premises (provided that Tenant shall not be responsible for making any structural changes to the Premises unless required due to
Tenant’s specific use of the Premises, as opposed to normal and customary office use), (ii) any Alterations made by Tenant to the Premises, or (iii) the Base Building, but as to the Base Building, only to the extent such obligations are
triggered by Tenant Improvements and Alterations made by or on behalf of Tenant to the Premises to the extent such Tenant Improvements or Alterations are not normal and customary business office improvements, or triggered by Tenant’s use of the
Premises for non-general office use (collectively, “Tenant’s Compliance With Law Obligations”). Should any standard or regulation now or hereafter be imposed on Landlord or Tenant by a
state, federal or local governmental body charged with the establishment, regulation and enforcement of occupational, health or safety standards for employers, employees, landlords or tenants, then Tenant agrees, at its sole cost and expense, to
comply promptly with such standards or regulations. Tenant shall be responsible, at its sole cost and expense, to make all alterations to the Premises as are required to comply with Tenant’s Compliance With Law Obligations. The judgment of any
court of competent jurisdiction or the admission of Tenant in any judicial action, regardless of whether Landlord is a party thereto, that Tenant has violated any of said governmental measures, shall be conclusive of that fact as between Landlord
and Tenant. For purposes of Section 1938 of the California Civil Code, Landlord hereby discloses to Tenant, and Tenant hereby acknowledges, that the Project, Building and Premises have not undergone inspection by a Certified Access Specialist
(CASp). As required by Section 1938(e) of the California Civil Code, Landlord hereby states as follows: “A Certified Access Specialist (CASp) can inspect the subject premises and determine whether the subject premises comply with all of
the applicable construction-related accessibility standards under state law. Although state law does not require a CASp inspection of the subject premises, the commercial property owner or lessor may not prohibit the lessee or tenant from obtaining
a CASp inspection of the subject premises for the occupancy or potential occupancy of the lessee or tenant, if requested by the lessee or tenant. The parties shall mutually agree on the arrangements for the time and manner of the CASp inspection,
the 

  

					
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[Synthorx Inc.]

 
payment of the fee for the CASp inspection, and the cost of making any repairs necessary to correct violations of construction-related accessibility standards within the premises.” In
furtherance of the foregoing, Landlord and Tenant hereby agree as follows: (a) any CASp inspection requested by Tenant shall be conducted, at Tenant’s sole cost and expense, by a CASp approved in advance by Landlord; and (b) subject
to this Article 24, Tenant, at its cost, is responsible for making any repairs within the Premises to correct violations of construction-related accessibility standards; and, if anything done by or for Tenant in its use or occupancy of the
Premises shall require repairs to the Building (outside the Premises) to correct violations of construction-related accessibility standards, then Tenant shall, at Landlord’s option, either perform such repairs at Tenant’s sole cost and
expense or reimburse Landlord upon demand, as Additional Rent, for the cost to Landlord of performing such repairs. 
 24.2
Landlord’s Compliance with Law Obligations. Landlord shall comply with all applicable laws relating to the Base Building and Common Areas, provided that compliance with such applicable laws is not the responsibility of Tenant
under this Lease, and provided further that Landlord’s failure to comply therewith would prohibit Tenant from obtaining or maintaining a certificate of occupancy for the Premises, or would unreasonably and materially affect the safety of
Tenant’s employees or create a significant health hazard for Tenant’s employees. Landlord shall be permitted to include in Operating Expenses any costs or expenses incurred by Landlord under this Article 24 to the extent not
prohibited by the terms of Section 4.2.3 above 
 25. LATE CHARGES If any installment of Rent or any other sum due from
Tenant shall not be received by Landlord or Landlord’s designee within five (5) business days after Tenant’s receipt of written notice from Landlord that said amount is due, then Tenant shall pay to Landlord a late charge equal to
five percent (5%) of the overdue amount plus any reasonable attorneys’ fees incurred by Landlord by reason of Tenant’s failure to pay Rent and/or other charges when due hereunder. The late charge shall be deemed Additional Rent and the
right to require it shall be in addition to all of Landlord’s other rights and remedies hereunder or at law and shall not be construed as liquidated damages or as limiting Landlord’s remedies in any manner. In addition to the late charge
described above, any Rent or other amounts owing hereunder which are not paid within ten (10) days after the date they are due shall bear interest from the date when due until paid at a rate per annum equal to the lesser of (i) the annual
“Bank Prime Loan” rate cited in the Federal Reserve Statistical Release Publication G.13(415), published on the first Tuesday of each calendar month (or such other comparable index as Landlord and Tenant shall reasonably agree upon if such
rate ceases to be published) plus four (4) percentage points, and (ii) the highest rate permitted by applicable law. 
 26. LANDLORD’S
RIGHT TO CURE DEFAULT; PAYMENTS BY TENANT 
 26.1 Landlord’s Cure. All covenants and agreements to be kept or
performed by Tenant under this Lease shall be performed by Tenant at Tenant’s sole cost and expense and without any reduction of Rent, except to the extent, if any, otherwise expressly provided herein. If Tenant shall fail to perform any
obligation under this Lease, and such failure shall continue in excess of the time allowed under Section 19.1.2, above, Landlord may, but shall not be obligated to, make any such payment or perform any such act on
Tenant’s part without waiving its rights based upon any default of Tenant and without releasing Tenant from any obligations hereunder. 

26.2 Tenant’s Reimbursement. Except as may be specifically provided to the contrary in this Lease, Tenant shall pay to
Landlord, within ten (10) business days of delivery by Landlord to Tenant of statements therefor: (i) sums equal to expenditures reasonably made and obligations incurred by Landlord in connection with the remedying by Landlord of an Event
of Default by Tenant pursuant to the provisions of Section 26.1; (ii) sums equal to all losses, costs, liabilities, damages and expenses referred to in Article 10 of this Lease; and (iii) sums equal to all
expenditures made and obligations incurred by Landlord in collecting or attempting to collect the Rent or in enforcing or attempting to enforce any rights of Landlord under this Lease or pursuant to law, including, without limitation, all reasonable
legal fees and other amounts so expended. Tenant’s obligations under this Section 26.2 shall survive the expiration or sooner termination of the Lease Term. 

27. ENTRY BY LANDLORD Landlord reserves the right at all reasonable times and upon at least twenty-four (24) hours’ prior written notice
(which may be delivered via email) to Tenant (except in the case of an emergency) to enter the Premises to (i) inspect them; (ii) show the Premises to prospective purchasers, or to current or prospective mortgagees, ground or underlying
lessors or insurers or, during the last twelve (12) months of the Lease Term, to prospective tenants; (iii) post notices of nonresponsibility (to the extent applicable pursuant to then applicable

  

					
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law); or (iv) alter, improve or repair the Premises or the Building, or for structural alterations, repairs or improvements to the Building or the Building’s systems and equipment. In
exercising the entry rights set forth in this Section, Landlord shall use commercially reasonable efforts to minimize interference with the conduct of Tenant’s business in connection with such entries into the Premises. Landlord may make any
such entries without the abatement of Rent, except as otherwise provided in this Lease, and may take such reasonable steps as required to accomplish the stated purposes. In an emergency, Landlord shall have the right to use any means that Landlord
may deem proper to open the doors in and to the Premises. Except in the case of an emergency, Tenant shall have the opportunity to have a representative of Tenant accompany the entrant, provided that Landlord shall not be required to delay any such
entrance due to the unavailability of Tenant’s representative. Any entry into the Premises by Landlord in the manner hereinbefore described shall not be deemed to be a forcible or unlawful entry into, or a detainer of, the Premises, or an
actual or constructive eviction of Tenant from any portion of the Premises. In making any such entry (other than in an emergency) ,Landlord shall use commercially reasonable efforts to cooperate with those certain safety and security measures
delivered to Landlord by Tenant prior to the date hereof. 
 28. TENANT PARKING Tenant shall have the right to use the amount of parking set forth in
Section 9 of the Summary, in the on-site and/or off-site, as the case may be, parking facility (or facilities) which serve the Project. Tenant shall abide by
all reasonable rules and regulations which are prescribed from time to time for the orderly operation and use of the parking facility where the parking passes are located (including any sticker or other identification system established by Landlord
and the prohibition of vehicle repair and maintenance activities in the parking facilities), and shall cooperate in seeing that Tenant’s employees and visitors also comply with such rules and regulations. During the Lease Term (including the
Option Term), such parking spaces shall be provided at no additional charge to Tenant (other than Operating Expenses to the extent allowed by the terms of Section 4.2.4 of this Lease); provided that Tenant shall also be responsible for
the full amount of any taxes imposed by any governmental authority in connection with the renting of such parking passes by Tenant or the use of the parking facility by Tenant. Tenant’s use of the Project parking facility shall be at
Tenant’s sole risk and Tenant acknowledges and agrees that Landlord shall have no liability whatsoever for damage to the vehicles of Tenant, its employees and/or visitors, or for other personal injury or property damage or theft relating to or
connected with the parking rights granted herein or any of Tenant’s, its employees’ and/or visitors’ use of the parking facilities. 
 29.
MISCELLANEOUS PROVISIONS 
 29.1 Terms; Captions. The words “Landlord” and “Tenant” as
used herein shall include the plural as well as the singular. The necessary grammatical changes required to make the provisions hereof apply either to corporations or partnerships or individuals, men or women, as the case may require, shall in all
cases be assumed as though in each case fully expressed. The captions of Articles and Sections are for convenience only and shall not be deemed to limit, construe, affect or alter the meaning of such Articles and Sections. 

29.2 Binding Effect. Subject to all other provisions of this Lease, each of the covenants, conditions and provisions of this
Lease shall extend to and shall, as the case may require, bind or inure to the benefit not only of Landlord and of Tenant, but also of their respective heirs, personal representatives, successors or assigns, provided this clause shall not permit any
assignment by Tenant contrary to the provisions of Article 14 of this Lease. 
 29.3 No Air Rights. No rights to any
view or to light or air over any property, whether belonging to Landlord or any other person, are granted to Tenant by this Lease. If at any time any windows of the Premises are temporarily darkened or the light or view therefrom is obstructed by
reason of any repairs, improvements, maintenance or cleaning in or about the Project, the same shall be without liability to Landlord and without any reduction or diminution of Tenant’s obligations under this Lease. 

29.4 Modification of Lease. Should any current or prospective mortgagee or ground lessor for the Building or Project require a
modification of this Lease, which modification will not cause an increased cost or expense to Tenant or in any other way materially and adversely change the rights and obligations of Tenant hereunder, then and in such event, Tenant agrees that this
Lease may be so modified and agrees to execute whatever commercially reasonable documents are reasonably required therefor and to deliver the same to Landlord within ten (10) business days following a request therefor. At the request of
Landlord or any mortgagee or ground lessor, Tenant agrees to 

  

					
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execute a short form of Lease and deliver the same to Landlord within ten (10) business days following the request therefor. 

29.5 Transfer of Landlord’s Interest. Tenant acknowledges that Landlord has the right to transfer all or any portion of its
interest in the Project or Building and in this Lease, and Tenant agrees that in the event of any such transfer, Landlord shall automatically be released from all liability accruing under this Lease after the date of such transfer and Tenant agrees
to look solely to such transferee for the performance of Landlord’s obligations accruing hereunder after the date of transfer, provided that such transferee has, in writing, fully assumed liability for all obligations of this Lease to be
performed by Landlord, including the return of any Security Deposit, and Tenant shall attorn to such transferee. 
 29.6 Prohibition
Against Recording. Except as provided in Section 29.4 of this Lease, neither this Lease, nor any memorandum, affidavit or other writing with respect thereto, shall be recorded by Tenant or by anyone acting through,
under or on behalf of Tenant. 
 29.7 Landlord’s Title. Landlord’s title is and always shall be paramount to the
title of Tenant. Nothing herein contained shall empower Tenant to do any act which can, shall or may encumber the title of Landlord. 
 29.8
Relationship of Parties. Nothing contained in this Lease shall be deemed or construed by the parties hereto or by any third party to create the relationship of principal and agent, partnership, joint venturer or any association between
Landlord and Tenant. 
 29.9 Application of Payments. Landlord shall have the right to apply payments received from Tenant
pursuant to this Lease, regardless of Tenant’s designation of such payments, to satisfy any obligations of Tenant hereunder, in such order and amounts as Landlord, in its sole discretion, may elect. 

29.10 Time of Essence. Time is of the essence with respect to the performance of every provision of this Lease in which time of
performance is a factor. 
 29.11 Partial Invalidity. If any term, provision or condition contained in this Lease shall, to any
extent, be invalid or unenforceable, the remainder of this Lease, or the application of such term, provision or condition to persons or circumstances other than those with respect to which it is invalid or unenforceable, shall not be affected
thereby, and each and every other term, provision and condition of this Lease shall be valid and enforceable to the fullest extent possible permitted by law. 

29.12 No Warranty. In executing and delivering this Lease, Tenant has not relied on any representations, including, but not
limited to, any representation as to the amount of any item comprising Additional Rent or the amount of the Additional Rent in the aggregate or that Landlord is furnishing the same services to other tenants, at all, on the same level or on the same
basis, or any warranty or any statement of Landlord which is not set forth herein or in one or more of the exhibits attached hereto. 
 29.13
Landlord Exculpation. The liability of Landlord or the Landlord Parties to Tenant for any default by Landlord under this Lease or arising in connection herewith or with Landlord’s operation, management, leasing, repair,
renovation, alteration or any other matter relating to the Project or the Premises shall be limited solely and exclusively to an amount which is equal to the interest of Landlord in the Building. Neither Landlord, nor any of the Landlord Parties
shall have any personal liability therefor, and Tenant hereby expressly waives and releases such personal liability on behalf of itself and all persons claiming by, through or under Tenant. The limitations of liability contained in this
Section 29.13 shall inure to the benefit of Landlord’s and the Landlord Parties’ present and future partners, beneficiaries, officers, directors, trustees, shareholders, agents and employees, and their respective
partners, heirs, successors and assigns. Under no circumstances shall any present or future partner of Landlord (if Landlord is a partnership), or trustee or beneficiary (if Landlord or any partner of Landlord is a trust), have any liability for the
performance of Landlord’s obligations under this Lease. Notwithstanding any contrary provision herein, neither Landlord nor the Landlord Parties shall be liable under any circumstances for injury or damage to, or interference with,
Tenant’s business, including but not limited to, loss of profits, loss of rents or other revenues, loss of business opportunity, loss of goodwill or loss of use, in each case, however occurring, or loss to inventory, scientific research,

  

					
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scientific experiments, laboratory animals, products, specimens, samples, and/or scientific, business, accounting and other records of every kind and description kept at the premises and any and
all income derived or derivable therefrom. 
 29.14 Entire Agreement. It is understood and acknowledged that there are no oral
agreements between the parties hereto affecting this Lease and this Lease constitutes the parties’ entire agreement with respect to the leasing of the Premises and supersedes and cancels any and all previous negotiations, arrangements,
brochures, agreements and understandings, if any, between the parties hereto or displayed by Landlord to Tenant with respect to the subject matter thereof, and none thereof shall be used to interpret or construe this Lease. None of the terms,
covenants, conditions or provisions of this Lease can be modified, deleted or added to except in writing signed by the parties hereto. 

29.15 Right to Lease. Landlord reserves the absolute right to effect such other tenancies in the Project as Landlord in the
exercise of its sole business judgment shall determine to best promote the interests of the Building or Project. Tenant does not rely on the fact, nor does Landlord represent, that any specific tenant or type or number of tenants shall, during the
Lease Term, occupy any space in the Building or Project. 
 29.16 Force Majeure. Any prevention, delay or stoppage due to
strikes, lockouts, labor disputes, acts of God, acts of war, terrorist acts, inability to obtain services, labor, or materials or reasonable substitutes therefor, governmental actions, civil commotions, fire or other casualty, and other causes
beyond the reasonable control of the party obligated to perform, except with respect to the obligations imposed with regard to Rent and other charges to be paid by Tenant pursuant to this Lease (collectively, a “Force Majeure”),
notwithstanding anything to the contrary contained in this Lease, shall excuse the performance of such party for a period equal to any such prevention, delay or stoppage and, therefore, if this Lease specifies a time period for performance of an
obligation of either party, that time period shall be extended by the period of any delay in such party’s performance caused by a Force Majeure. 

29.17 Waiver of Redemption by Tenant. Tenant hereby waives, for Tenant and for all those claiming under Tenant, any and all
rights now or hereafter existing to redeem by order or judgment of any court or by any legal process or writ, Tenant’s right of occupancy of the Premises after any termination of this Lease. 

29.18 Notices. All notices, demands, statements, designations, approvals or other communications (collectively,
“Notices”) given or required to be given by either party to the other hereunder or by law shall be in writing, shall be (A) sent by United States certified or registered mail, postage prepaid, return receipt requested
(“Mail”), (B) transmitted by telecopy, if such telecopy is promptly followed by a Notice sent by Mail, (C) delivered by a nationally recognized overnight courier, or (D) delivered personally. Any Notice shall be sent,
transmitted, or delivered, as the case may be, to Tenant at the appropriate address set forth in Section 10 of the Summary, or to such other place as Tenant may from time to time designate in a Notice to Landlord, or to
Landlord at the addresses set forth below, or to such other places as Landlord may from time to time designate in a Notice to Tenant. Any Notice will be deemed given (i) three (3) days after the date it is posted if sent by Mail, (ii) the
date the telecopy is transmitted, (iii) the date the overnight courier delivery is made, or (iv) the date personal delivery is made. As of the date of this Lease, any Notices to Landlord must be sent, transmitted, or delivered, as the case
may be, to the following addresses: 
 HCP Torrey Pines, LLC., 

c/o HCP, Inc. 
 462 Stevens
Avenue, Suite 107 
 Solana Beach, California 92075 

with a copy to: 
 HCP Torrey
Pines, LLC., 
 c/o HCP, Inc. 

1920 Main Street, Suite 1200 

Irvine, CA 92614 
 Attn: Legal
Department 

  

					
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[Synthorx Inc.]

 and 

Allen Matkins Leck Gamble Mallory & Natsis LLP 

1901 Avenue of the Stars, Suite 1800 

Los Angeles, California 90067 

29.19 Joint and Several. If there is more than one tenant, the obligations imposed upon Tenant under this Lease shall be joint
and several. 
 29.20 Authority. If either Landlord or Tenant is a corporation, trust or partnership, each individual executing
this Lease on behalf of Landlord or Tenant, as applicable, hereby represents and warrants that such party is a duly formed and existing entity qualified to do business in the State of California and that such party has full right and authority to
execute and deliver this Lease and that each person signing on behalf of Tenant is authorized to do so. In such event, Tenant shall, within ten (10) days after execution of this Lease, deliver to Landlord satisfactory evidence of such authority
and, if a corporation, upon demand by Landlord no more than one time during the Lease Term (except in connection with an Event of Default), also deliver to Landlord satisfactory evidence of (i) good standing in Tenant’s state of
incorporation and (ii) qualification to do business in the State of California. 
 29.21 Attorneys’ Fees. In the
event that either Landlord or Tenant should bring suit for the possession of the Premises, for the recovery of any sum due under this Lease, or because of the breach of any provision of this Lease or for any other relief against the other, then all
costs and expenses, including reasonable attorneys’ fees, incurred by the prevailing party therein shall be paid by the other party, which obligation on the part of the other party shall be deemed to have accrued on the date of the commencement
of such action and shall be enforceable whether or not the action is prosecuted to judgment. 
 29.22 Governing Law; WAIVER OF TRIAL BY
JURY. This Lease shall be construed and enforced in accordance with the laws of the State of California. IN ANY ACTION OR PROCEEDING ARISING HEREFROM, LANDLORD AND TENANT HEREBY CONSENT TO (I) THE JURISDICTION OF ANY COMPETENT COURT
WITHIN THE STATE OF CALIFORNIA, (II) SERVICE OF PROCESS BY ANY MEANS AUTHORIZED BY CALIFORNIA LAW, AND (III) IN THE INTEREST OF SAVING TIME AND EXPENSE, TRIAL WITHOUT A JURY IN ANY ACTION, PROCEEDING OR COUNTERCLAIM BROUGHT BY EITHER OF
THE PARTIES HERETO AGAINST THE OTHER OR THEIR SUCCESSORS IN RESPECT OF ANY MATTER ARISING OUT OF OR IN CONNECTION WITH THIS LEASE, THE RELATIONSHIP OF LANDLORD AND TENANT, TENANT’S USE OR OCCUPANCY OF THE PREMISES, AND/OR ANY CLAIM FOR INJURY
OR DAMAGE, OR ANY EMERGENCY OR STATUTORY REMEDY. IN THE EVENT LANDLORD COMMENCES ANY SUMMARY PROCEEDINGS OR ACTION FOR NONPAYMENT OF BASE RENT OR ADDITIONAL RENT, TENANT SHALL NOT INTERPOSE ANY COUNTERCLAIM OF ANY NATURE OR DESCRIPTION (UNLESS SUCH
COUNTERCLAIM SHALL BE MANDATORY) IN ANY SUCH PROCEEDING OR ACTION, BUT SHALL BE RELEGATED TO AN INDEPENDENT ACTION AT LAW. 
 29.23
Submission of Lease. Submission of this instrument for examination or signature by Tenant does not constitute a reservation of, option for or option to lease, and it is not effective as a lease or otherwise until execution and delivery
by both Landlord and Tenant. 
 29.24 Brokers. Landlord and Tenant hereby warrant to each other that they have had no dealings
with any real estate broker or agent in connection with the negotiation of this Lease, excepting only the real estate brokers or agents specified in Section 12 of the Summary (the “Brokers”), and that they
know of no other real estate broker or agent who is entitled to a commission in connection with this Lease. Each party agrees to indemnify and defend the other party against and hold the other party harmless from any and all claims, demands, losses,
liabilities, lawsuits, judgments, costs and expenses (including without limitation reasonable attorneys’ fees) with respect to any leasing commission or equivalent compensation alleged to be owing on account of any dealings with any real estate
broker or agent, other than the Brokers, occurring by, through, or under the indemnifying party. The terms of this Section 29.24 shall survive the expiration or earlier termination of the Lease Term. 

  

					
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 29.25 Independent Covenants. This Lease shall be construed as though the
covenants herein between Landlord and Tenant are independent and not dependent and Tenant hereby expressly waives the benefit of any statute to the contrary and agrees that if Landlord fails to perform its obligations set forth herein, Tenant shall
not be entitled to make any repairs or perform any acts hereunder at Landlord’s expense or to any setoff of the Rent or other amounts owing hereunder against Landlord, except as expressly provided herein. 

29.26 Project or Building Name, Address and Signage. Landlord shall have the right at any time to change the name and/or address
of the Project or Building and to install, affix and maintain any and all signs on the exterior and on the interior of the Project or Building as Landlord may, in Landlord’s sole discretion, desire. Tenant shall not use the name of the Project
or Building or use pictures or illustrations of the Project or Building in advertising or other publicity or for any purpose other than as the address of the business to be conducted by Tenant in the Premises, without the prior written consent of
Landlord. 
 29.27 Counterparts; Electronic Signatures. This Lease may be executed in counterparts with the same effect as if
both parties hereto had executed the same document. Both counterparts shall be construed together and shall constitute a single lease. Delivery of an executed counterpart of this Lease by email shall be as effective as delivery of a manually
executed counterpart hereto. This Lease may be executed by a party’s signature transmitted by email, and copies of this Lease executed and delivered by means of emailed signatures shall have the same force and effect as copies executed and
delivered with original signatures. All parties hereto may rely upon emailed signatures (including signatures in Portable Document Format or DocuSign format) as if such signatures were originals. 

29.28 Confidentiality. Tenant acknowledges that the content of this Lease and any related documents are confidential information.
Except with respect to filings and disclosures required by applicable securities laws, Tenant shall keep such confidential information strictly confidential and shall not disclose such confidential information to any person or entity (other than
Tenant’s consultants, attorneys, property managers and employees that have a need to know such information), including any governmental authority, without the prior written consent of Landlord. In the event Tenant reasonably believes that
disclosure is required by applicable law, it shall provide Landlord ten (10) days’ advance notice of disclosure of confidential information so that Landlord may attempt to obtain a protective order. Tenant may additionally release such
information to bona fide prospective purchasers, lenders, assignees, or subtenants, subject to any such parties’ written agreement to be bound by the terms of this Section 29.28. 

29.29 Development of the Project. 

29.29.1 Subdivision. Landlord reserves the right to subdivide all or a portion of the buildings and Common Areas. Tenant agrees
to execute and deliver, upon demand by Landlord and in the form reasonably requested by Landlord, any additional commercially reasonable documents needed to conform this Lease to the circumstances resulting from a subdivision and any all maps in
connection therewith. Notwithstanding anything to the contrary set forth in this Lease, the separate ownership of any buildings and/or Common Areas by an entity other than Landlord shall not affect the calculation of Direct Expenses or Tenant’s
payment of Tenant’s Share of Direct Expenses. 
 29.29.2 Construction of Property and Other Improvements. Tenant
acknowledges that portions of the Project may be under construction following Tenant’s occupancy of the Premises, and that such construction may result in levels of noise, dust, obstruction of access, etc. which are in excess of that present in
a fully constructed project. Tenant hereby waives any and all rent offsets or claims of constructive eviction which may arise in connection with such construction; provided, however, in undertaking any such construction, Landlord shall use
commercially reasonable efforts to minimize interference with Tenant’s use and enjoyment of the Premises, Tenant’s access to the Premises, or any other rights Tenant has under this Lease. 

29.30 No Violation. Each of Landlord and Tenant hereby warrants and represents to the other that neither its execution of nor
performance under this Lease shall cause it to be in violation of any agreement, instrument, contract, law, rule or regulation by which it is bound, and each of Landlord and Tenant shall protect, defend, indemnify and hold the other harmless against
any claims, demands, losses, damages, liabilities, costs and expenses, including, without limitation, reasonable attorneys’ fees and costs, arising from its breach of this warranty and representation. 

  

					
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 29.31 Transportation Management. Tenant shall fully comply with all present or
future governmentally-mandated programs intended to manage parking, transportation or traffic in and around the Project and/or the Building, and in connection therewith, Tenant shall take responsible action for the transportation planning and
management of all employees located at the Premises by working directly with Landlord, any governmental transportation management organization or any other transportation-related committees or entities. Such programs may include, without limitation:
(i) restrictions on the number of peak-hour vehicle trips generated by Tenant; (ii) increased vehicle occupancy; (iii) implementation of an in-house ridesharing program and an employee
transportation coordinator; (iv) working with employees and any Project, Building or area-wide ridesharing program manager; (v) instituting employer-sponsored incentives (financial or in-kind) to
encourage employees to rideshare; and (vi) utilizing flexible work shifts for employees. 
 [Signatures appear on following page]

  

					
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[Synthorx Inc.]

 IN WITNESS WHEREOF, Landlord and Tenant have caused this Lease to be executed the day and
date first above written. 
  

			
	 LANDLORD:
  

HCP TORREY PINES, LLC.,
a Delaware limited liability company
  

By: /s/ Michael
Dorris                                

 
 Michael
Dorris                                        
    

                          
      Print Name
  
 Its: Vice
President                                        

	  	 TENANT:
  

SYNTHORX INC.,
 a Delaware corporation

 
 By: /s/ Laura
Shawver                                

 
 Laura
Shawver                                        
    

                          
      Print Name
  
 Its: President and
CEO                                    

  

					
		  	-43-	  	 HCP TORREY PINES, LLC

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[Synthorx Inc.]

 EXHIBIT A 

11099 NORTH TORREY PINES ROAD 

OUTLINE OF PREMISES 
  

 

  

					
		  	 EXHIBIT A

-1-
	  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

 EXHIBIT A-1 

11099 NORTH TORREY PINES ROAD 

PROJECT SITE PLAN 
  

 

  

					
		  	 EXHIBIT A-1

-1-
	  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

 EXHIBIT B 

11099 NORTH TORREY PINES ROAD 

TENANT WORK LETTER 

This Tenant Work Letter shall set forth the terms and conditions relating to the construction of the tenant improvements in the Premises. This
Tenant Work Letter is essentially organized chronologically and addresses the issues of the construction of the Premises, in sequence, as such issues will arise during the actual construction of the Premises. All references in this Tenant Work
Letter to Articles or Sections of “this Lease” shall mean the relevant portion of Articles 1 through 29 of the Lease to which this Tenant Work Letter is attached as
Exhibit B and of which this Tenant Work Letter forms a part, and all references in this Tenant Work Letter to Sections of “this Tenant Work Letter” shall mean the relevant portion of
Sections 1 through 6 of this Tenant Work Letter. 
 SECTION 1 

CONSTRUCTION DRAWINGS FOR THE PREMISES 

Landlord and Tenant have approved that certain space plan for the Premises, attached hereto as Schedule 1 to Exhibit B
(collectively, the “Space Plan”). Following Tenant’s execution and delivery of this Lease, Tenant shall continue to cooperate in good faith with Landlord’s architects and engineers to supply such information as is
necessary to allow the Landlord’s architects and engineers to complete the architectural and engineering drawings for the Premises, and the final architectural working drawings in a form which is complete to allow subcontractors to bid on the
work and to obtain all applicable permits and in a manner consistent with, and which are a logical extension of, the Space Plan (as reasonably determined by Landlord) and otherwise in accordance with Building standards (the “Working
Drawings”). Landlord shall supply Tenant with electronic copies of the Working Drawings within three (3) business days of their completion. Tenant shall advise Landlord within two (2) business days after Tenant’s receipt of
such copies of the Working Drawings if Tenant reasonably believes the same are not materially consistent with the Space Plan or incomplete in any material respect. If Landlord is so advised, Landlord shall promptly cause the Working Drawings to be
revised to make them materially consistent with, or a logical extension of, the Space Plan. Landlord shall then re-submit the revised Working Drawings to Tenant in the format prescribed above, and Tenant shall
thereafter respond within one (1) business day after Tenant’s receipt of such copies of the Working Drawings if Tenant reasonably believes the same are not materially consistent with the Space Plan or incomplete in any material respect,
with the process repeating until Tenant approves or is deemed to have approved the Working Drawings (the “Approved Working Drawings”). Landlord shall construct the improvements in the Premises (the “Tenant
Improvements”) using Building standard methods, materials and finishes pursuant to the Approved Working Drawings. Tenant shall make no changes or modifications to (i) the Space Plan, or (ii) once completed, the Approved Working
Drawings, without the prior written consent of Landlord, which consent may be withheld in Landlord’s sole discretion if such change or modification would directly or indirectly delay the “Substantial Completion,” as that term is
defined in Section 5.1 of this Tenant Work Letter, of the Tenant Improvements or increase the cost of designing or constructing the Tenant Improvements, provided, however, that if Tenant agrees in writing that any such
delay shall be a “Tenant delay” subject to Section 5.2 of this Tenant Work Letter and/or Tenant agrees in writing to deposit such additional costs with Landlord, then Landlord shall not unreasonably withhold,
condition or delay its approval to such changes. The Tenant Improvements shall be constructed in accordance with Landlord’s Building standards, using Building standard methods, materials and finishes which are materially consistent with those
currently existing in the Premises. 
 SECTION 2 

OVER-ALLOWANCE AMOUNT 

In the event that after Tenant’s execution of this Lease, any revisions, changes, or substitutions shall be made by or on behalf of
Tenant (subject to Landlord’s approval) to (i) the Space Plan, (ii) the Approved Working Drawings (once the same are completed), or (iii) the Tenant Improvements, or in the event that Tenant requests revisions, changes, or
substitutions which cause the Approved Working Drawings to not be a logical extension of or consistent 

  

					
		  	 EXHIBIT B

-1-
	  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

 
with the Space Plan, or which require non-Building standard methods, materials or finishes, then any additional costs which arise in connection with such
revisions, changes or substitutions shall be paid by Tenant to Landlord within five (5) business days of Landlord’s written request. Upon Tenant’s request for any such change, Landlord shall provide an estimate of any increased costs
or delays resulting therefrom, and Tenant shall thereafter have one (1) business days to approve such change or withdraw its request. 

SECTION 3 

INTENTIONALLY OMITTED 

SECTION 4 

INTENTIONALLY OMITTED 

SECTION 5 

COMPLETION OF THE TENANT IMPROVEMENTS; 

LEASE COMMENCEMENT DATE 

5.1 Ready for Occupancy. The Premises shall be deemed “Ready for Occupancy” upon the Substantial Completion of
the Tenant Improvements. For purposes of this Lease, “Substantial Completion” of the Tenant Improvements shall occur upon the completion of construction of the Tenant Improvements in the Premises in a good, workmanlike manner and in
compliance with applicable laws, pursuant to the Approved Working Drawings (as reasonably determined by Landlord), with the exception of any punch list items and any tenant fixtures, work-stations (including any related fixture and/or equipment
electrification), built-in furniture, or equipment (including security and other Tenant systems) to be installed by Tenant or under the supervision of the contractor who constructs the Tenant Improvements (the
“Contractor”), and the receipt of a temporary certificate of occupancy, or it legal equivalent, for the Premises. “Punch list” items are limited to immaterial defects in the Tenant Improvements that do not prohibit
Tenant’s occupancy or unreasonably interfere with Tenant’s use of the Premises for the Permitted Use. Landlord shall promptly correct any punch list items in a reasonable time period and shall use commercially reasonable efforts to
minimize interference with Tenant’s use of the Premises in so correcting any punch list items. 
 5.2 Delay of the Substantial
Completion of the Tenant Improvements. Except as provided in this Section 5.2, the Lease Commencement Date shall occur as set forth in the Lease and Section 5.1, above. If there shall be a
delay or there are delays in the Substantial Completion of the Tenant Improvements or in the occurrence of any of the other conditions precedent to the Commencement Date, as set forth in of the Lease, as a direct, indirect, partial, or total result
of: 
 5.2.1 Tenant’s failure to timely approve any matter requiring Tenant’s approval; 

5.2.2 A breach by Tenant of the terms of this Tenant Work Letter or the Lease; 

5.2.3 Tenant’s request for changes in the Space Plan, the Tenant Improvements, or, once completed, the Approved Working Drawings, or
Tenant’s request for changes which cause the Approved Working Drawings to not be a logical extension of or consistent with the Space Plan or Tenant’s request for changes which require non-Building
standard methods, materials or finishes; 
 5.2.4 Tenant’s requirement for materials, components, finishes or improvements which are not
available in a commercially reasonable time given the anticipated date of Substantial Completion of the Tenant Improvements, as set forth in the Lease, or which are different from, or not included in, Landlord’s standard improvement package
items for the Building; 
 5.2.5 Changes to the base, shell and core work of the Building required by the Approved Working Drawings (provided
that this Section 5.2.5 shall not apply to the extent any such changes are already required by the Space Plan attached hereto); or 

  

					
		  	 EXHIBIT B

-2-
	  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

 5.2.6 Any other acts or omissions of Tenant, or its agents, or employees; 

then, notwithstanding anything to the contrary set forth in the Lease or this Tenant Work Letter and regardless of the actual date of the Substantial
Completion of the Tenant Improvements, the date of Substantial Completion of the Tenant Improvements shall be deemed to be the date the Substantial Completion of the Tenant Improvements would have occurred if no Tenant delay or delays, as set forth
above, had occurred; provided, however, that with respect to any delay under Section 5.2.6, above, Tenant shall have one (1) business day to cure such delay following Landlord’s notice to Tenant of such delay. 

SECTION 6 

MISCELLANEOUS 
 6.1
Tenant’s Entry Into the Premises Prior to Substantial Completion. Provided that Tenant and its agents do not interfere with Contractor’s work in the Building and the Premises, Contractor shall allow Tenant access to
the Premises at least thirty (30) days prior to the Substantial Completion of the Tenant Improvements for the purpose of Tenant installing furniture, equipment or fixtures (including Tenant’s data and telephone equipment) in the Premises.
Prior to Tenant’s entry into the Premises as permitted by the terms of this Section 6.1, Tenant shall submit a schedule to Landlord and Contractor, for their approval, which schedule shall detail the timing and purpose
of Tenant’s entry. Tenant shall hold Landlord harmless from and indemnify, protect and defend Landlord against any loss or damage to the Building or Premises and against injury to any persons caused by Tenant’s actions pursuant to this
Section 6.1. 
 6.2 Freight Elevators. Landlord shall, consistent with its obligations to other
tenants of the Building, make the freight elevator reasonably available to Tenant in connection with initial decorating, furnishing and moving into the Premises, at no additional cost to Tenant during normal business hours. With respect to
Tenant’s use of freight elevators after normal business hours, if so requested by Tenant, Tenant shall be required to pay for the incremental out-of-pocket costs
incurred by Landlord for after-hours access control personnel. 
 6.3 Tenant’s Representative. Tenant has designated Chris
Breitbarth as its sole representative with respect to the matters set forth in this Tenant Work Letter, who, until further notice to Landlord, shall have full authority and responsibility to act on behalf of the Tenant as required in this
Tenant Work Letter. 
 6.4 Landlord’s Representative. Landlord has designated Jeff Sobczyk as its sole representative with
respect to the matters set forth in this Tenant Work Letter, who, until further notice to Tenant, shall have full authority and responsibility to act on behalf of the Landlord as required in this Tenant Work Letter. 

6.5 Tenant’s Agents. All subcontractors, laborers, materialmen, and suppliers retained directly by Tenant shall all be union
labor in compliance with the then existing master labor agreements. 
 6.6 Time of the Essence in This Tenant Work Letter.
Unless otherwise indicated, all references herein to a “number of days” shall mean and refer to calendar days. In all instances where Tenant is required to approve or deliver an item, if no written notice of approval is given or the item
is not delivered within the stated time period, at Landlord’s sole option, at the end of such period the item shall automatically be deemed approved or delivered by Tenant and the next succeeding time period shall commence. 

6.7 Tenant’s Lease Default. Notwithstanding any provision to the contrary contained in this Lease, if an event of default as
described in the Lease, or a default by Tenant under this Tenant Work Letter, has occurred at any time on or before the Substantial Completion of the Tenant Improvements, then (i) in addition to all other rights and remedies granted to Landlord
pursuant to the Lease, Landlord shall have the right to cause the Contractor to cease the construction of the Tenant Improvements (in which case, Tenant shall be responsible for any delay in the Substantial Completion of the Tenant Improvements
caused by such work stoppage as set forth in Section 5.2 of this Tenant Work Letter), and (ii) all other obligations of Landlord under the terms of this Tenant Work Letter shall be forgiven until such time as such
default is cured pursuant to the terms of the Lease. 

  

					
		  	 EXHIBIT B

-3-
	  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

 6.8 Cooperation by Tenant. Tenant acknowledges that the timing of the
completion of the Approved Work Drawings and the Tenant Improvements is of the utmost importance to Landlord. Accordingly, Tenant hereby agrees to fully and diligently cooperate with all reasonable requests by Landlord in connection with or related
to the design and construction of the Tenant Improvements, and in connection therewith, shall respond to Landlord’s requests for information and/or approvals, except as specifically set forth herein to the contrary, within two (2) business
days following request by Landlord. 

  

					
		  	 EXHIBIT B

-4-
	  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

 SCHEDULE 1 TO EXHIBIT B 

SPACE PLAN 
  

 

  

					
		  	 EXHIBIT B

-5-
	  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

 EXHIBIT C 

11099 NORTH TORREY PINES ROAD 

NOTICE OF LEASE TERM DATES 
  

	To:	
                       
      

                       
      

                       
      

                       
      
  

	 	Re:	 Lease
dated                    , 20    
between                    ,
a                    (“Landlord”),
and                    , a                     
(“Tenant”) concerning Suite              on floor(s)
                    of the building located at
                    , California. 

Gentlemen: 
 In accordance with the Lease (the
“Lease”), we wish to advise you and/or confirm as follows: 
  

	 	1.	 The Lease Term shall commence on or has commenced on
                     for a term of
                         ending on
                    . 

  

	 	2.	 Rent commenced to accrue on
                    , in the amount of
                    . 

  

	 	3.	 If the Lease Commencement Date is other than the first day of the month, the first billing will contain a pro
rata adjustment. Each billing thereafter, with the exception of the final billing, shall be for the full amount of the monthly installment as provided for in the Lease. 

 

	 	4.	 Your rent checks should be made payable to
                     at                     .

  

	 	5.	 The exact number of rentable/usable square feet within the Premises is
                     square feet. 

  

	 	6.	 Tenant’s Share as adjusted based upon the exact number of usable square feet within the Premises is
                    %. 

  

	
	 “Landlord”:
  

                          
                                         
              ,

a                          
                                         
             
  

By:                         
                                         
          

Its:                      
                                         
     

  

					
		  	 EXHIBIT C

-1-
	  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

	
	 Agreed to and Accepted as

of             , 20     .

 
 “Tenant”:

 

                   
                                         
                        

a                   
                                         
                      
  

By:                  
                                         
                   

      Its:            
                                         
                    

  

					
		  	 EXHIBIT C

-2-
	  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

 EXHIBIT D 

11099 NORTH TORREY PINES ROAD 

FORM OF TENANT’S ESTOPPEL CERTIFICATE 

The undersigned as Tenant under that certain Lease (the “Lease”) made and entered into as of
                    , 20        by and between
                    as Landlord, and the undersigned as Tenant, for Premises consisting of the entire office building located at
                    , California, certifies as follows: 

1. Attached hereto as Exhibit A is a true and correct copy of the Lease and all amendments and
modifications thereto. The documents contained in Exhibit A represent the entire agreement between the parties as to the Premises. 

2. The undersigned currently occupies the Premises described in the Lease, the Lease Term commenced on
                    , and the Lease Term expires on
                    , and the undersigned has no option to terminate or cancel the Lease or to purchase all or any part of the Premises, the Building
and/or the Project, except as expressly provided in the Lease. 
 3. Base Rent became payable on
                    . 
 4. The Lease is
in full force and effect and has not been modified, supplemented or amended in any way except as provided in Exhibit A. 

5. Tenant has not transferred, assigned, or sublet any portion of the Premises nor entered into any license or concession agreements with
respect thereto except as follows: 
 6. Tenant shall not modify the documents contained in
Exhibit A without the prior written consent of Landlord’s mortgagee. 
 7. All monthly
installments of Base Rent, all Additional Rent and all monthly installments of estimated Additional Rent have been paid when due through
                    . The current monthly installment of Base Rent is
$                    . 
 8. To
Tenant’s knowledge, all conditions of the Lease to be performed by Landlord necessary to the enforceability of the Lease have been satisfied and Landlord is not in default thereunder. In addition, the undersigned has not delivered any notice to
Landlord regarding a default by Landlord thereunder. The Lease does not require Landlord to provide any rental concessions or to pay any leasing brokerage commissions, which have not already been provided or paid. 

9. No rental has been paid more than thirty (30) days in advance and no security has been deposited with Landlord except as provided in
the Lease. 
 10. To Tenant’s knowledge, as of the date hereof, there are no existing defenses or offsets, or claims or any basis for a
claim, that the undersigned has against Landlord. 
 11. If Tenant is a corporation or partnership, each individual executing this Estoppel
Certificate on behalf of Tenant hereby represents and warrants that Tenant is a duly formed and existing entity qualified to do 

  

					
		  	 EXHIBIT D

-1-
	  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

 
business in California and that Tenant has full right and authority to execute and deliver this Estoppel Certificate and that each person signing on behalf of Tenant is authorized to do so. 

12. There are no actions pending against the undersigned under the bankruptcy or similar laws of the United States or any state. 

13. To Tenant’s knowledge, Tenant is in full compliance with all federal, state and local laws, ordinances, rules and regulations
affecting its use of the Premises, including, but not limited to, those laws, ordinances, rules or regulations relating to hazardous or toxic materials. Tenant has never permitted or suffered, nor does Tenant have any knowledge of, the generation,
manufacture, treatment, use, storage, disposal or discharge of any hazardous, toxic or dangerous waste, substance or material in, on, under or about the Premises in violation of any federal, state or local law, ordinance, rule or regulation. 

14. To the undersigned’s knowledge, all tenant improvement work to be performed by Landlord under the Lease has been completed in
accordance with the Lease and has been accepted by the undersigned and all reimbursements and allowances due to the undersigned under the Lease in connection with any tenant improvement work have been paid in full. All work (if any) in the common
areas required by the Lease to be completed by Landlord has been completed and all parking spaces required by the Lease have been furnished and/or all parking ratios required by the Lease have been met. 

The undersigned acknowledges that this Estoppel Certificate may be delivered to Landlord or to a prospective mortgagee or prospective
purchaser, and acknowledges that said prospective mortgagee or prospective purchaser will be relying upon the statements contained herein in making the loan or acquiring the property of which the Premises are a part and that receipt by it of this
certificate is a condition of making such loan or acquiring such property. 
 Executed at
                    on the        day
of                    , 20    . 
  

	
	 “Tenant”:
  

_______________________________________,

a______________________________________
  

By: ___________________________________

      Its: ________________________________
  

By: ___________________________________

      Its: ________________________________

  

  

					
		  	  
 EXHIBIT D

-2-
	  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

 EXHIBIT E 

11099 NORTH TORREY PINES ROAD 

ENVIRONMENTAL QUESTIONNAIRE 

ENVIRONMENTAL QUESTIONNAIRE 

FOR COMMERCIAL AND INDUSTRIAL PROPERTIES 

Tenant Name: 
 Lease Address: 

 

			
	Lease Type (check correct box – right click to properties):	  	☐ Primary Lease/Lessee
		  	☐ Sublease from: ________________

 Instructions: The following questionnaire is to be completed by the Lessee representative with knowledge of the
planned operations for the specified building/location. Please print clearly and attach additional sheets as necessary. 
  

	1.0	 PROCESS INFORMATION 

Describe planned site use, including a brief description of manufacturing processes and/or pilot plants planned for this site, if any. 

___________________________________________________________________________________________________ 

___________________________________________________________________________________________________ 

___________________________________________________________________________________________________ 

 

	2.0	 HAZARDOUS MATERIALS – OTHER THAN WASTE 

Will (or are) non-waste hazardous materials be/being used or stored at this site? If so, continue with
the next question. If not, go to Section 3.0. 
  

	 	2.1	 Are any of the following materials handled on the
Property?            ☐  Yes    ☐  No 

[A material is handled if it is used, generated, processed, produced, packaged, treated, stored, emitted, discharged, or disposed.] If
YES, check (right click to properties) the applicable correct Fire Code hazard categories below. 
  

											
	☐	 	Combustible dusts/fibers	 	☐	 	Explosives	 	☐	 	Flammable liquids
	☐	 	Combustible liquids (e.g., oils)	 	☐	 	Compressed gas - inert	 	☐	 	Flammable solids/pyrophorics
	☐	 	Cryogenic liquids - inert	 	☐	 	Compressed gas - flammable/pyrophoric	 	☐	 	Organic peroxides
	☐	 	Cryogenic liquids - flammable	 	☐	 	Compressed gas - oxidizing	 	☐	 	Oxidizers - solid or liquid
	☐	 	Cryogenic liquids - oxidizing	 	☐	 	Compressed gas - toxic	 	☐	 	Reactives - unstable or water reactive
	☐	 	Corrosives - solid or liquid	 	☐	 	Compressed gas - corrosive	 	☐	 	Toxics - solid or liquid

  

	 	2-2.	 For all materials checked in Section 2.1 above, please list the specific material(s), use(s), and
quantities of each used or stored on the site in the table below; or attach a separate inventory. NOTE: If proprietary, the constituents need not be named but the hazard information and volumes are required. 

 

  

					
		  	 EXHIBIT E

-1-
	  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

											
	 Material/

Chemical
	 	 Physical State (Solid,
Liquid, or Gas)
	 	 Container Size
	  	 Number of
Containers Used &
Stored
	  	 Total Quantity
	  	 Units (pounds for
solids, gallons or
liters for liquids,
&
cubic feet for gases)

		 		 		  		  		  	
		 		 		  		  		  	

  

	 	2-3.	 Describe the planned storage area location(s) for the materials in
Section 2-2 above. Include site maps and drawings as appropriate. 

___________________________________________________________________________________________ 

___________________________________________________________________________________________ 

 

	 	2-4.	 Other hazardous materials. Check below (right click to properties) if applicable. NOTE: If either of
the latter  

  

					
		  	  
 EXHIBIT E

-2-
	  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

	 	
two are checked (BSL-3 and/or radioisotope/radiation), be advised that not all lease locations/cities or lease agreements allow these hazards; and if
either of these hazards are planned, additional information will be required with copies of oversight agency authorizations/licenses as they become available. 

 

											
	☐	 	Risk Group 2/Biosafety Level-2 Biohazards	 	☐	 	Risk Group 3/Biosafety Level-3 Biohazards	 	☐	 	Radioisotopes/Radiation

  

	3.0	 HAZARDOUS WASTE (i.e., REGULATED CHEMICAL WASTE) 

Are (or will) hazardous wastes (be) generated?        ☐ Yes    ☐ No

 If YES, continue with the next question. If not, skip this section and go to section 4.0. 

 

	 	3.1	 Are or will any of the following hazardous (CHEMICAL) wastes generated, handled, or disposed of (where
applicable and allowed) on the property? 

  

											
	☐	 	Liquids	 	☐	 	Process sludges	 	☐	 	PCBs
	☐	 	Solids	 	☐	 	Metals	 	☐	 	wastewater

  

	 	3-2.	 List and estimate the quantities of hazardous waste identified in Question
3-1 above. 

  

											
	 HAZRDOUS (CHEMICAL)

WASTE GENERATED
	  	 SOURCE
	  	 WASTE TYPE
	  	 APPROX.
MONTHLY
QUANTITY
with
units
	  	
DISPOSITION [e.g., off-site

landfill, incineration, fuel
blending scrap metal;
wastewater neutralization
(onsite or
off-site)]

	  	 RCRA
listed
(federal)
	  	
Non-RCRA
(California
ONLY or
recycle)

		  		  	☐	  	☐	  		  	
		  		  	☐	  	☐	  		  	
		  		  	☐	  	☐	  		  	
		  		  	☐	  	☐	  		  	
		  		  	☐	  	☐	  		  	

  

	 	3-3.	 Waste characterization by:        Process knowledge
☐        EPA lab analysis ☐        Both ☐ 

  

	 	3-4.	 Please include name, location, and permit number (e.g. EPA ID No.) for transporter and disposal facility if
applicable. Attach separate pages as necessary. If not yet known, write “TBD.” 

  

							
	 Hazardous Waste

Transporter/Disposal Facility Name
	 	 Facility Location
	 	 Transporter (T) or

Disposal (D) Facility
	  	 Permit Number

		 		 		  	
		 		 		  	
		 		 		  	

  

	 	3-5.	 Are pollution controls or monitoring employed in the process to prevent or minimize the release of wastes into
the environment? NOTE: This does NOT mean fume hoods; examples include air scrubbers, cyclones, carbon or HEPA filters at building exhaust fans, sedimentation tanks, pH neutralization systems for wastewater, etc. 

☐   Yes    ☐  No 

If YES, please list/describe: ___________________________________________________________ 

 

                       
                                         
                                         
                                         
                   

                       
                                         
                                         
                                         
                   

  

					
		  	 EXHIBIT E

-3-
	  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

	4.0	 OTHER REGULATED WASTE (i.e., REGULATED BIOLOGICAL WASTE, referred to as “Medical Waste” in
California) 

  

	 	4-1.	 Will (or do) you generate medical waste?    ☐ Yes    ☐
No    If NO, skip to Section 5.0. 

  

	 	4-2.	 Check the types of waste that will be generated, all of which fall under the California Medical Waste Act:

  

											
	☐	 	Contaminated sharps (i.e., if contaminated with 3 Risk Group 2 materials)	 	☐	 	Animal carcasses	 	☐	 	Pathology waste known or suspected to be contaminated with 3 Risk Group 2 pathogens)
						
	☐	 	Red bag biohazardous waste (i.e., with 3 Risk Group 2 materials) for autoclaving	 	☐	 	 Human or non-human primate blood, tissues, etc.

(e.g., clinical specimens)
	 	☐	 	Trace Chemotherapeutic Waste and/or Pharmaceutical waste NOT otherwise regulated as RCRA chemical waste

  

	 	4-3.	 What vendor will be used for off-site autoclaving and/or incineration?

	 	                                  
                                         
                                         
                                         
   	 

  

	 	4-5.	 Do you have a Medical Waste Permit for this site?    ☐
Yes    ☐ No, not required. 

                     
                                         
            ☐ No, but an application will be submitted. 
  

	5.0	 UNDERGROUND STORAGE TANKS (USTS) & ABOVEGROUND STORAGE TANKS (ASTS) 

 

	 	5-1.	 Are underground storage tanks (USTs), aboveground storage tanks (ASTs), or associated pipelines used for the
storage of petroleum products, chemicals, or liquid wastes present on site (lease renewals) or required for planned operations (new tenants)?    ☐ Yes    ☐ No 

NOTE: If you will have your own diesel emergency power generator, then you will have at least one AST! [NOTE: If a backup generator
services multiple tenants, then the landlord usually handles the permits.] 
 If NO, skip to section 6.0. If YES, please describe
capacity, contents, age, type of the USTs or ASTs, as well any associated leak detection/spill prevention measures. Please attach additional pages if necessary. 
  

											
	 UST or AST
	 	 Capacity (gallons)
	 	 Contents
	  	 Year Installed
	  	 Type (Steel,
Fiberglass, etc.)
	  	 Associated Leak
Detection /
Spill
Prevention
Measures*

		 		 		  		  		  	
		 		 		  		  		  	
		 		 		  		  		  	

  

	 	*NOTE:	 The following are examples of leak detection / spill prevention measures: integrity testing, inventory
reconciliation, leak detection system, overfill spill protection, secondary containment, cathodic protection. 

  

	 	5-2.	 Please provide copies of written tank integrity test results and/or monitoring documentation, if available.

  

	 	5-3.	 Is the UST/AST registered and permitted with the appropriate regulatory
agencies?    ☐ Yes    ☐ No, not yet 

 If YES, please attach a copy of
the required permit(s). See Section 7-1 for the oversight agencies that issue permits, with the exception of those for diesel emergency power generators which are permitted by the local
Air Quality District (Bay Area Air Quality Management District = BAAQMD; or San Diego Air Pollution Control District = San Diego APCD). 
  

	 	5-4.	 If this Questionnaire is being completed for a lease renewal, and if any of the USTs/ASTs have leaked,

  

					
		  	  
 EXHIBIT E

-4-
	  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

 
please state the substance released, the media(s) impacted (e.g., soil, water, asphalt, etc.), the actions taken, and all remedial responses to the incident. 

_________________________________________________________________________________________ 

_________________________________________________________________________________________ 

_________________________________________________________________________________________ 

 

	 	5-5.	 If this Questionnaire is being completed for a lease renewal, have USTs/ASTs been removed from the Property?

 ☐ Yes    ☐ No 

If YES, please provide any official closure letters or reports and supporting documentation (e.g., analytical test results, remediation report
results, etc.). 
  

	 	5-6.	 For Lease renewals, are there any above or below ground pipelines on site used to transfer chemicals or wastes?

 ☐ Yes    ☐ No 

For new tenants, are installations of this type required for the planned operations?    ☐
Yes    ☐ No 
 If YES to either question in this section 5-6, please
describe. 
 _________________________________________________________________________________________ 

_________________________________________________________________________________________ 

_________________________________________________________________________________________ 

 

	6.0	 ASBESTOS CONTAINING BUILDING MATERIALS 

Please be advised that an asbestos survey may have been performed at the Property. If provided, please review the information that identifies
the locations of known asbestos containing material or presumed asbestos containing material. All personnel and appropriate subcontractors should be notified of the presence of these materials, and informed not to disturb these materials. Any
activity that involves the disturbance or removal of these materials must be done by an appropriately trained individual/contractor. 
  

	7.0	 OTHER REGULATORY PERMITS/REQUIREMENTS 

 

	 	7-1.	 Does the operation have or require an industrial wastewater permit to discharge into the local National
Pollutant Discharge Elimination System (NPDES)? [Example: This applies when wastewater from equipment cleaning is routed through a pH neutralization system prior to discharge into the sanitary or lab sewer for certain pharmaceutical manufacturing
wastewater; etc.] Permits are obtained from the regional sanitation district that is treating wastewater. 

 ☐
Yes    ☐ No    ☐ No, but one will be prepared and submitted to the Landlord property management company. 

If so, please attach a copy of this permit or provide it later when it has been prepared. 

 

	 	7-2.	 Has a Hazardous Materials Business Plan (HMBP) been developed for the site and submitted via the State of
California Electronic Reporting System (CERS)? [NOTE: The trigger limits for having to do this are 3 200 cubic feet if any one type of compressed gas(except for carbon
dioxide and inert simple asphyxiant gases, which have a higher trigger limit of 3 1,000 cubic feet); 3
55 gallons if any one type of hazardous chemical liquid; and 3500 pounds of any one type of hazardous chemical solid. So a full-sixe gas cylinder and a 260-liter of liquid nitrogen are triggers! Don’t forget the diesel fuel in a backup emergency generator if the diesel tank size is 3 55
gallons and it is permitted under the tenant (rather than under the landlord).] NOTE: Each local Certified Unified Program Agency (CUPA) in California governs the HMBP process so start there. Examples: the CUPA for cities in San Mateo County is
the County Environmental Health Department; the CUPA for the City of Hayward, CA is the Hayward Fire Department; the CUPA for Mountain View is the Mountain View Fire Department; and, the CUPA for San Diego is the County of San Diego Hazardous
Materials Division (HMD), 

  

  

					
		  	 EXHIBIT E

-5-
	  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

 ☐ Yes    ☐ No, not required. ☐ No, but one will be
prepared and submitted, and a copy will be provided to the landlord property management company. 
 If one has been completed, please attach
a copy. Continue to provide updated versions as they are completed. This is a legal requirement in that State law requires that the owner/operator of a business located on leased or rented real property shall notify, in writing, the owner of the
property that the business is subject to and is in compliance with the Hazardous Materials Business Plan requirements (Health and Safety Code Chapter 6.95 Section 25505.1). 

 

	 	7-3.	 NOTE: Please be advised that if you are involved in any tenant improvements that require a construction
permit, you will be asked to provide the local city with a Hazardous Materials Inventory Statement (HMIS) to ensure that your hazardous chemicals fall within the applicable Fire Code fire control area limits for the applicable construction occupancy
of the particular building. The HMIS will include much of the information listed in Section 2-2. Neither the landlord nor the landlord’s property management company expressly warrants that the
inventory provided in Section 2-2 will necessarily meet the applicable California Fire Code fire control area limits for building occupancy, especially in shared tenant occupancy situations. It is the
responsibility of the tenant to ensure that a facility and site can legally handle the intended operations and hazardous materials desired/ needed for its operations, but the landlord is happy to assist in this determination when possible.

 CERTIFICATION 
 I am
familiar with the real property described in this questionnaire. By signing below, I represent and warrant that the answers to the above questions are complete and accurate to the best of my knowledge. I also understand that Lessor will rely on the
completeness and accuracy of my answers in assessing any environmental liability risks associated with the property. 
  

	
	 Signature: ______________________

	
	 Name: ______________________

	
	 Title: ______________________

	
	 Date: ______________________

	
	Telephone: ______________________

  

					
		  	 EXHIBIT E

-6-
	  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

 LEASE 

11099 NORTH TORREY PINES ROAD 

HCP TORREY PINES, LLC., 
 a
Delaware limited liability company, 
 as Landlord, 

and 
 SYNTHORX INC., 

a Delaware corporation, 
 as
Tenant. 

  

					
		  		  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

 TABLE OF CONTENTS 

 

							
	 	  	 	  	Page	 
	1.	  	 PREMISES, BUILDING, PROJECT, AND COMMON AREAS
	  	 	4	 
	2.	  	 LEASE TERM; OPTION TERM
	  	 	5	 
	3.	  	 BASE RENT
	  	 	6	 
	4.	  	 ADDITIONAL RENT
	  	 	7	 
	5.	  	 USE OF PREMISES
	  	 	13	 
	6.	  	 SERVICES AND UTILITIES
	  	 	17	 
	7.	  	 REPAIRS
	  	 	19	 
	8.	  	 ADDITIONS AND ALTERATIONS
	  	 	20	 
	9.	  	 COVENANT AGAINST LIENS
	  	 	21	 
	10.	  	 INSURANCE
	  	 	22	 
	11.	  	 DAMAGE AND DESTRUCTION
	  	 	24	 
	12.	  	 NONWAIVER
	  	 	25	 
	13.	  	 CONDEMNATION
	  	 	26	 
	14.	  	 ASSIGNMENT AND SUBLETTING
	  	 	26	 
	15.	  	 SURRENDER OF PREMISES; OWNERSHIP AND REMOVAL OF TRADE FIXTURES
	  	 	30	 
	16.	  	 HOLDING OVER
	  	 	31	 
	17.	  	 ESTOPPEL CERTIFICATES
	  	 	31	 
	18.	  	 SUBORDINATION
	  	 	31	 
	19.	  	 DEFAULTS; REMEDIES
	  	 	32	 
	20.	  	 COVENANT OF QUIET ENJOYMENT
	  	 	34	 
	21.	  	 SECURITY DEPOSIT
	  	 	34	 
	22.	  	 COMMUNICATIONS AND COMPUTER LINE
	  	 	35	 
	23.	  	 SIGNS
	  	 	35	 
	24.	  	 COMPLIANCE WITH LAW
	  	 	35	 
	25.	  	 LATE CHARGES
	  	 	36	 
	26.	  	 LANDLORD’S RIGHT TO CURE DEFAULT; PAYMENTS BY TENANT
	  	 	36	 
	27.	  	 ENTRY BY LANDLORD
	  	 	36	 
	28.	  	 TENANT PARKING
	  	 	37	 
	29.	  	MISCELLANEOUS PROVISIONS	  	 	37	 

 EXHIBITS 
  

			
	A	  	 OUTLINE OF PREMISES

	B	  	 TENANT WORK LETTER

	C	  	 FORM OF NOTICE OF LEASE TERM DATES

	D	  	 FORM OF TENANT’S ESTOPPEL CERTIFICATE

	E	  	ENVIRONMENTAL QUESTIONNAIRE

  

					
		  	(i)	  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

 INDEX 

 

					
	 	  	Page(s)	 
	 Abatement Event
	  	 	34	 
	 Affiliate
	  	 	29	 
	 Alterations
	  	 	20	 
	 Base Rent
	  	 	6	 
	 Brokers
	  	 	40	 
	 Building
	  	 	4	 
	 Common Areas
	  	 	4	 
	 Contemplated Effective Date
	  	 	28	 
	 Contemplated Transfer Space
	  	 	28	 
	 Direct Expenses
	  	 	7	 
	 Eligibility Period
	  	 	34	 
	 Estimate
	  	 	12	 
	 Estimate Statement
	  	 	12	 
	 Estimated Direct Expenses
	  	 	12	 
	 Expense Year
	  	 	7	 
	 Force Majeure
	  	 	39	 
	 Generator
	  	 	19	 
	 HVAC
	  	 	17	 
	 Intention to Transfer Notice
	  	 	28	 
	 Landlord
	  	 	1	 
	 Landlord Parties
	  	 	22	 
	 Landlord Repair Notice
	  	 	24	 
	 Landlord’s Hazardous Materials
	  	 	15	 
	 Lease
	  	 	1	 
	 Lease Commencement Date
	  	 	5	 
	 Lease Expiration Date
	  	 	5	 
	 Lease Term
	  	 	5	 
	 Lease Year
	  	 	5	 
	 Lines
	  	 	35	 
	 Mail
	  	 	39	 
	 Management Fee Cap
	  	 	10	 
	 Nine Month Period
	  	 	28	 
	 Notices
	  	 	39	 
	 Operating Expenses
	  	 	7	 
	 Original Improvements
	  	 	23	 
	 Permitted Transfer
	  	 	29	 
	 Permitted Transferee
	  	 	29	 
	 Permitted Transferee Assignee.
	  	 	29	 
	 Premises
	  	 	4	 
	 Project,
	  	 	4	 
	 Security Deposit
	  	 	34	 
	 Statement
	  	 	11	 
	 Subject Space
	  	 	26	 
	 Summary
	  	 	1	 
	 Tax Expenses
	  	 	10	 
	 Tenant
	  	 	1	 
	 Tenant Parties
	  	 	22	 
	 Tenant Work Letter
	  	 	1	 
	 Tenant’s Repair Obligations
	  	 	19	 
	 Tenant’s Share
	  	 	11	 

  

					
		  	(ii)	  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]

					
	 	  	Page(s)	 
	 Transfer Notice
	  	 	26	 
	 Transferee
	  	 	26	 

  

					
		  	(iii)	  	 HCP TORREY PINES, LLC

[11099 NORTH TORREY PINES ROAD]

[Synthorx Inc.]EXHIBIT
10.1

 

WRITTEN
CONSENT OF DIRECTORS TO CORPORATE ACTION

WITHOUT
MEETING OF PHI GROUP, INC.

 

The
undersigned, being all of the directors of the Board of Directors of PHI Group, Inc., a Nevada corporation (the “Company”),
hereby adopt the following resolutions in lieu of a meeting on this 8th day of November 2018.

 

WHEREAS,
on April 23, 2018 the Company’s Board of Directors passed a resolution to declare a twenty percent (20%) special stock
dividend from its holdings of Common Stock in American Pacific Resources, Inc., a subsidiary of the Company, to shareholders of
Common Stock of the Company as follows: (a) Declaration date: April 23, 2018; (b) Record date: May 31, 2018; (c) Payment date:
October 31, 2018; (d) Dividend ratio: All eligible shareholders of Common Stock of the Company as of the Record date shall be
entitled to receive two (2) shares of Common Stock of American Pacific Resources, Inc. for every ten (10) shares of Common Stock
of PHI Group, Inc. held by such shareholders as of the referenced Record date;

 

WHEREAS,
on October 31, 2018, the Company’s Board of Directors extended the Payment Date of the special stock dividend to March
29, 2019 to allow for substantive developments of American Pacific Resources, Inc. before filing a registration statement with
the Securities and Exchange Commission to take this subsidiary public.

 

WHEREAS,
it deems to be in the best interests of the Company and its shareholders to amend the Record Date and the dividend ratio to
allow for a broader participation of the Company’s shareholders in the special dividend distribution.

 

NOW,
THEREFORE, BE IT RESOLVED, that the Company amend the new dividend ratio and the new Record Date as follows: (a) Eligible
shareholders: In order to be eligible for the above-mentioned special stock dividend, the minimum amount of Common Stock of PHI
Group, Inc. each shareholder must hold as of the New Record Date is twenty (20) shares; (b) New Record Date: The new Record Date
will March 01, 2019, subject to FINRA’s approval; (c) New dividend ratio: All eligible shareholders of Common Stock of the
Company as of the new Record Date shall be entitled to receive one (1) share of Common Stock of American Pacific Resources, Inc.
for every twenty (20) shares of Common Stock of PHI Group, Inc. held by such shareholders as of the new Record date; and (d) Payment
Date: The Payment Date for the afore-mentioned special stock dividend is March 29, 2019;

 

FURTHER
RESOLVED that in addition to and without limiting the foregoing, each officer of the Company be and hereby is authorized and
directed to take, or cause to be taken, such further action, and to execute and deliver, or cause to be delivered, for and in
the name and on behalf of the Company, all such instruments and documents as such officer may deem necessary, appropriate or in
the best interests of the Company to effectuate the intent of the foregoing resolutions and the transactions contemplated thereby
(as conclusively evidenced by the taking of such actions or the execution and delivery of such instruments and documents, as the
case may be) and all action heretofore taken by such officer in connection with the subject of the foregoing recitals and resolutions
be, and it hereby is, approved, ratified and confirmed in all respects as the act and deed of the Company.

 

    	 	Page 1 of 2	 

    	 

    

 

By
their signatures below, the above resolutions have been duly authorized and adopted by the Company’s Board of Directors.

 

	/s/
    Tam Bui	 	/s/
    Henry D. Fahman
	Tam
    Bui, Director	 	Henry
    D. Fahman, Director
	 	 	 
	/s/
    Frank Hawkins	 	 
	Frank
    Hawkins, Director	 	 

 

    	 	Page 2 of 2

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