Document:

EX-4.1

 Exhibit 4.1 
  

 
  

AMENDED AND RESTATED INVESTORS’ RIGHTS AGREEMENT 

 TABLE OF CONTENTS 

 

									
	 	 	 	  	 	  	Page	 
	 1.         
	 	 Definitions
	  	 	1	 
			
	 2.
	 	 Registration Rights
	  	 	4	 
		 	 2.1
	  	 Demand Registration
	  	 	4	 
		 	 2.2
	  	 Company Registration
	  	 	6	 
		 	 2.3
	  	 Underwriting Requirements
	  	 	6	 
		 	 2.4
	  	 Obligations of the Company
	  	 	7	 
		 	 2.5
	  	 Furnish Information
	  	 	9	 
		 	 2.6
	  	 Expenses of Registration
	  	 	9	 
		 	 2.7
	  	 Delay of Registration
	  	 	9	 
		 	 2.8
	  	 Indemnification
	  	 	10	 
		 	 2.9
	  	 Reports Under Exchange Act
	  	 	12	 
		 	 2.10
	  	 Limitations on Subsequent Registration Rights
	  	 	12	 
		 	 2.11
	  	 “Market Stand-off” Agreement
	  	 	12	 
		 	 2.12
	  	 Restrictions on Transfer
	  	 	13	 
		 	 2.13
	  	 Termination of Registration Rights
	  	 	14	 
			
	 3.
	 	 Information and Observer Rights
	  	 	15	 
		 	 3.1
	  	 Delivery of Financial Statements
	  	 	15	 
		 	 3.2
	  	 Inspection
	  	 	16	 
		 	 3.3
	  	 Observer
	  	 	16	 
		 	 3.4
	  	 Termination of Information
	  	 	17	 
		 	 3.5
	  	 Confidentiality
	  	 	17	 
			
	 4.
	 	 Rights to Future Stock Issuances
	  	 	17	 
		 	 4.1
	  	 Right of First Offer
	  	 	17	 
		 	 4.2
	  	 Termination
	  	 	19	 
			
	 5.
	 	 Additional Covenants
	  	 	19	 
		 	 5.1
	  	 Insurance
	  	 	19	 
		 	 5.2
	  	 Employee Agreements
	  	 	19	 
		 	 5.3
	  	 Employee Stock
	  	 	19	 
		 	 5.4
	  	 Matters Requiring Investor Director Approval
	  	 	20	 
		 	 5.5
	  	 Board Matters
	  	 	20	 
		 	 5.6
	  	 Successor Indemnification
	  	 	20	 
		 	 5.7
	  	 Indemnification Matters
	  	 	20	 
		 	 5.8
	  	 Termination of Covenants
	  	 	21	 
			
	 6.
	 	 Miscellaneous
	  	 	21	 
		 	 6.1
	  	 Successors and Assigns
	  	 	21	 
		 	 6.2
	  	 Governing Law
	  	 	21	 
		 	 6.3
	  	 Counterparts
	  	 	22	 
		 	 6.4
	  	 Titles and Subtitles
	  	 	22	 

  
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	 	 6.5
	  	 Notices
	  	 	22	 
		 	 6.6
	  	 Amendments and Waivers
	  	 	22	 
		 	 6.7
	  	 Severability
	  	 	23	 
		 	 6.8
	  	 Aggregation of Stock
	  	 	23	 
		 	 6.9
	  	 Additional Investors
	  	 	23	 
		 	 6.10
	  	 Entire Agreement
	  	 	23	 
		 	 6.11
	  	 Dispute Resolution
	  	 	23	 
		 	 6.12
	  	 Delays or Omissions
	  	 	23	 
		
	 Schedule A
	  	– Schedule of Investors	  

  
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 AMENDED AND RESTATED INVESTORS’ RIGHTS AGREEMENT 

THIS AMENDED AND RESTATED INVESTORS’ RIGHTS AGREEMENT (this “Agreement”), is made as of the 2nd day of March, 2020, by and among Keros Therapeutics, Inc., a Delaware corporation (the “Company”), and each of the investors listed on Schedule A hereto, each of which is
referred to in this Agreement as an “Investor”. 
 RECITALS 

WHEREAS, certain of the Investors (the “Existing Investors”) hold shares of the Company’s Series A Preferred
Stock, Series A-1 Preferred Stock, Series B-1 Preferred Stock and/or shares of Common Stock issued upon conversion thereof and possess registration rights, information
rights, rights of first offer, and other rights pursuant to an Amended and Restated Investors’ Rights Agreement dated as of November 9, 2018 between the Company and such Investors (the “Prior Agreement”); 

WHEREAS, certain Existing Investors desire to amend and restate the Prior Agreement in its entirety and to accept the rights created
pursuant to this Agreement in lieu of the rights granted to them under the Prior Agreement; and 
 WHEREAS, certain Investors are
parties to that certain Series C Preferred Stock Purchase Agreement of even date herewith between the Company and certain of the Investors (the “Purchase Agreement”), under which certain of the Company’s and such
Investors’ obligations are conditioned upon the execution and delivery of this Agreement by such Investors, certain Existing Investors and the Company. 

NOW, THEREFORE, the Existing Investors hereby agree that the Prior Agreement shall be amended and restated and replaced in its entirety
by this Agreement, and the parties to this Agreement further agree as follows: 
 1. Definitions. For purposes of this
Agreement: 
 1.1 “Affiliate” means, with respect to any specified Person, any other Person who, directly or indirectly,
controls, is controlled by, or is under common control with such Person, including without limitation any general partner, managing member, officer or director of such Person or any venture capital fund now or hereafter existing that is controlled
by one or more general partners or managing members of, or shares the same management company with, such Person. 
 1.2 “Common
Stock” means shares of the Company’s common stock, par value $0.0001 per share. 
 1.3 “Competitor” means a
Person engaged, directly or indirectly (including through any partnership, limited liability company, corporation, joint venture or similar arrangement (whether now existing or formed hereafter)), in the same or similar business as the
Company, but shall not include any financial investment firm or collective investment vehicle that, together with its Affiliates, holds less than twenty percent (20)% of the outstanding equity of any Competitor and does not, nor do any of its
Affiliates, have a right to designate any members of the Board of 

 
Directors of any Competitor; provided, however, that neither (i) Foresite Capital Fund IV, L.P. and its Affiliates, (ii) OrbiMed and its Affliates, (iii) Pontifax and
its Affiliates nor (iv) Global Health Science Fund II, L.P. shall be deemed Competitors. 
 1.4 “Damages” means any
loss, damage, claim or liability (joint or several) to which a party hereto may become subject under the Securities Act, the Exchange Act, or other federal or state law, insofar as such loss, damage, claim or liability (or any action in respect
thereof) arises out of or is based upon: (a) any untrue statement or alleged untrue statement of a material fact contained in any registration statement of the Company, including any preliminary prospectus or final prospectus contained therein
or any amendments or supplements thereto; (b) an omission or alleged omission to state therein a material fact required to be stated therein, or necessary to make the statements therein not misleading; or (c) any violation or alleged
violation by the indemnifying party (or any of its agents or Affiliates) of the Securities Act, the Exchange Act, any state securities law, or any rule or regulation promulgated under the Securities Act, the Exchange Act, or any state
securities law. 
 1.5 “Derivative Securities” means any securities or rights convertible into, or exercisable or
exchangeable for (in each case, directly or indirectly), Common Stock, including options and warrants. 
 1.6 “Exchange
Act” means the Securities Exchange Act of 1934, as amended, and the rules and regulations promulgated thereunder. 
 1.7
“Excluded Registration” means (a) a registration relating to the sale of securities to employees of the Company or a subsidiary pursuant to a stock option, stock purchase, equity incentive or similar plan; (b) a
registration relating to an SEC Rule 145 transaction; (c) a registration on any form that does not include substantially the same information as would be required to be included in a registration statement covering the sale of the Registrable
Securities; or (d) a registration in which the only Common Stock being registered is Common Stock issuable upon conversion of debt securities that are also being registered. 

1.8 “Form S-1” means such form under the Securities Act as in effect on the
date hereof or any successor registration form under the Securities Act subsequently adopted by the SEC. 
 1.9 “Form S-3” means such form under the Securities Act as in effect on the date hereof or any registration form under the Securities Act subsequently adopted by the SEC that permits incorporation of substantial
information by reference to other documents filed by the Company with the SEC. 
 1.10 “GAAP” means generally accepted
accounting principles in the United States. 
 1.11 “Holder” means any holder of Registrable Securities who is a party to
this Agreement. 
 1.12 “Immediate Family Member” means a child, stepchild, grandchild, parent, stepparent, grandparent,
spouse, sibling, mother-in-law, father-in-law, son-in-law, daughter-in- law, brother-in-law, or sister-in-law, including, adoptive relationships, of a natural person referred to herein. 

  
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 1.13 “Initiating Holders” means, collectively, Holders who properly
initiate a registration request under this Agreement. 
 1.14 “IPO” means the Company’s first underwritten public
offering of its Common Stock under the Securities Act. 
 1.15 “Key Employee” means any executive-level employee
(including, division director and vice president-level positions) as well as any employee who, either alone or in concert with others, develops, invents, programs, or designs any Company Intellectual Property (as defined in the Purchase Agreement).

 1.16 “Major Investor” means any Investor that, individually or together with such Investor’s Affiliates, holds at
least 100,000 shares of Registrable Securities (as adjusted for any stock split, stock dividend, combination, or other recapitalization or reclassification effected after the date hereof). 

1.17 “New Securities” means, collectively, equity securities of the Company, whether or not currently authorized, as well as
rights, options, or warrants to purchase such equity securities, or securities of any type whatsoever that are, or may become, convertible or exchangeable into or exercisable for such equity securities. 

1.18 “Orbimed” means OrbiMed Private Investments VII, LP, The Biotech Growth Trust PLC and OrbiMed Genesis Master Fund, LP.

 1.19 “Person” means any individual, corporation, partnership, trust, limited liability company, association or other
entity. 
 1.20 “Pontifax” means any Pontifax (Israel) IV, L.P., Pontifax (Cayman) IV, L.P., Pontifax (China) IV,
L.P. and Pontifax Late Stage Fund L.P. 
 1.21 “Preferred Director” means any director of the Company that
the holders of record of the Series A Preferred Stock, Series B-1 Preferred Stock or Series C Preferred Stock are entitled to elect pursuant to the Company’s Certificate of Incorporation. 

1.22 “Preferred Stock” means, collectively, shares of Series A Preferred Stock, Series
A-1 Preferred Stock, Series B-1 Preferred Stock and Series C Preferred Stock. 

1.23 “Registrable Securities” means (i) the Common Stock issuable or issued upon conversion of the Preferred
Stock; (ii) any Common Stock, or any Common Stock issued or issuable (directly or indirectly) upon conversion and/or exercise of any other securities of the Company, now held or acquired by the
Investors after the date hereof; and (iii) any Common Stock issued as (or issuable upon the conversion or exercise of any warrant, right, or other security that is issued as) a dividend or other distribution with respect to, or in exchange for
or in replacement of, the shares referenced in clauses (i) and (ii) above; excluding in all cases, however, any Registrable Securities sold by a Person in a transaction in which the applicable rights under this

  
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Agreement are not assigned pursuant to Subsection 6.1, and excluding for purposes of Section 2 any shares for which registration rights have terminated pursuant to
Subsection 2.13 of this Agreement. 
 1.24 “Registrable Securities then outstanding” means
the number of shares determined by adding the number of shares of outstanding Common Stock that are Registrable Securities and the number of shares of Common Stock issuable (directly or indirectly) pursuant to then exercisable and/or
convertible securities that are Registrable Securities. 
 1.25 “Restricted Securities” means the securities of the Company
required to be notated with the legend set forth in Subsection 2.12(b) hereof. 
 1.26 “SEC”
means the Securities and Exchange Commission. 
 1.27 “SEC Rule 144” means Rule 144 promulgated by the SEC under the
Securities Act. 
 1.28 “SEC Rule 145” means Rule 145 promulgated by the SEC under the Securities Act. 

1.29 “Securities Act” means the Securities Act of 1933, as amended, and the rules and regulations promulgated thereunder.

 1.30 “Selling Expenses” means all underwriting discounts, selling commissions, and stock transfer taxes applicable to
the sale of Registrable Securities, and fees and disbursements of counsel for any Holder, except for the fees and disbursements of the Selling Holder Counsel borne and paid by the Company as provided in Subsection 2.6. 

1.31 “Series A Preferred Stock” means shares of the Company’s Series A Preferred Stock, par
value $0.0001 per share. 
 1.32 “Series A-1 Preferred Stock” means shares of the Company’s
Series A-1 Preferred Stock, par value $0.0001 per share. 
 1.33 “Series B-1 Preferred
Stock” means shares of the Company’s Series B-1 Preferred Stock, par value $0.0001 per share. 

1.34 “Series C Preferred Stock” means shares of the Company’s Series C Preferred Stock, par value $0.0001 per
share. 
 1.35 “Voting Agreement” means that certain Amended and Restated Voting Agreement by and between the Company and
certain stockholders of the Company, dated on or about the date hereof. 
 2. Registration Rights. The Company covenants and agrees as
follows: 
 2.1 Demand Registration. 

  
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 (a) Form S-1 Demand. If at any time after one
hundred eighty (180) days after the effective date of the registration statement for the IPO, the Company receives a request from Holders of at least a majority of the Registrable Securities then outstanding that the Company file a Form S-1 registration statement with respect to the Registrable Securities of such Holders having an anticipated aggregate offering price, net of Selling Expenses, of at least $25 million, then the Company
shall (x) within ten (10) days after the date such request is given, give notice thereof (the “Demand Notice”) to all Holders other than the Initiating Holders; and (y) as soon as practicable, and in any event within
sixty (60) days after the date such request is given by the Initiating Holders, file a Form S-1 registration statement under the Securities Act covering all Registrable Securities that the Initiating
Holders requested to be registered and any additional Registrable Securities requested to be included in such registration by any other Holders, as specified by notice given by each such Holder to the Company within twenty (20) days of
the date the Demand Notice is given, and in each case, subject to the limitations of Subsections 2.1(c) and 2.3. 

(b) Form S-3 Demand. If at any time when it is eligible to use a Form S-3 registration statement, the Company receives a request from Holders of at least twenty percent (20%) of the Registrable Securities then outstanding that the Company file a Form
S-3 registration statement with respect to outstanding Registrable Securities of such Holders having an anticipated aggregate offering price, net of Selling Expenses, of at least $3 million, then the
Company shall (i) within ten (10) days after the date such request is given, give a Demand Notice to all Holders other than the Initiating Holders; and (ii) as soon as practicable, and in any event within forty-five (45) days
after the date such request is given by the Initiating Holders, file a Form S-3 registration statement under the Securities Act covering all Registrable Securities requested to be included in such registration
by any other Holders, as specified by notice given by each such Holder to the Company within twenty (20) days of the date the Demand Notice is given, and in each case, subject to the limitations of Subsections 2.1(c) and 2.3.

 (c) Notwithstanding the foregoing obligations, if the Company furnishes to Holders requesting a registration pursuant to this
Subsection 2.1 a certificate signed by the Company’s chief executive officer stating that in the good faith judgment of the Company’s Board of Directors it would be materially detrimental to the Company and its
stockholders for such registration statement to either become effective or remain effective for as long as such registration statement otherwise would be required to remain effective, because such action would (i) materially interfere with a
significant acquisition, corporate reorganization, or other similar transaction involving the Company; (ii) require premature disclosure of material information that the Company has a bona fide business purpose for preserving as confidential;
or (iii) render the Company unable to comply with requirements under the Securities Act or Exchange Act, then the Company shall have the right to defer taking action with respect to such filing, and any time periods with respect to filing or
effectiveness thereof shall be tolled correspondingly, for a period of not more than sixty (60) days after the request of the Initiating Holders is given; provided, however, that the Company may not invoke this right more than once in
any twelve (12) month period; and provided further that the Company shall not register any securities for its own account or that of any other stockholder during such sixty (60) day period other than an Excluded Registration. 

(d) The Company shall not be obligated to effect, or to take any action to effect, any registration pursuant to
Subsection 2.1(a) (i) during the period that is sixty (60) days before the Company’s good faith estimate of the date of filing of, and ending on a date that is one hundred 

  
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eighty (180) days after the effective date of, a Company-initiated registration, provided, that the Company is actively employing in good faith commercially reasonable efforts to
cause such registration statement to become effective; (ii) after the Company has effected two registrations pursuant to Subsection 2.1(a); or (iii) if the Initiating Holders propose to dispose of shares of
Registrable Securities that may be immediately registered on Form S-3 pursuant to a request made pursuant to Subsection 2.1(b). The Company shall not be obligated to effect, or to
take any action to effect, any registration pursuant to Subsection 2.1(b) (i) during the period that is thirty (30) days before the Company’s good faith estimate of the date of filing of, and ending on a date
that is ninety (90) days after the effective date of, a Company-initiated registration, provided, that the Company is actively employing in good faith commercially reasonable efforts to cause such registration statement to become
effective; or (ii) if the Company has effected two registrations pursuant to Subsection 2.1(b) within the twelve (12) month period immediately preceding the date of such request. A registration shall not be
counted as “effected” for purposes of this Subsection 2.1(d) until such time as the applicable registration statement has been declared effective by the SEC, unless the Initiating Holders withdraw their request
for such registration, elect not to pay the registration expenses therefor, and forfeit their right to one demand registration statement pursuant to Subsection 2.6, in which case such withdrawn registration statement shall
be counted as “effected” for purposes of this Subsection 2.1(d). 
 2.2 Company Registration. If
the Company proposes to register (including, for this purpose, a registration effected by the Company for stockholders other than the Holders) any of its securities under the Securities Act in connection with the public offering of such securities
solely for cash (other than in an Excluded Registration), the Company shall, at such time, promptly give each Holder notice of such registration. Upon the request of each Holder given within twenty (20) days after such notice is given by the
Company, the Company shall, subject to the provisions of Subsection 2.3, cause to be registered all of the Registrable Securities that each such Holder has requested to be included in such registration. The Company shall
have the right to terminate or withdraw any registration initiated by it under this Subsection 2.2 before the effective date of such registration, whether or not any Holder has elected to include Registrable Securities in
such registration. The expenses (other than Selling Expenses) of such withdrawn registration shall be borne by the Company in accordance with Subsection 2.6. 

2.3 Underwriting Requirements. 

(a) If, pursuant to Subsection 2.1, the Initiating Holders intend to distribute the Registrable Securities
covered by their request by means of an underwriting, they shall so advise the Company as a part of their request made pursuant to Subsection 2.1, and the Company shall include such information in the Demand Notice. The
underwriter(s) will be selected by the Company and shall be reasonably acceptable to a majority in interest of the Initiating Holders. In such event, the right of any Holder to include such Holder’s Registrable Securities in such registration
shall be conditioned upon such Holder’s participation in such underwriting and the inclusion of such Holder’s Registrable Securities in the underwriting to the extent provided herein. All Holders proposing to distribute their securities
through such underwriting shall (together with the Company as provided in Subsection 2.4(e)) enter into an underwriting agreement in customary form with the underwriter(s) selected for such underwriting. Notwithstanding any
other provision of this Subsection 2.3, if the managing underwriter(s) advise(s) the Initiating Holders in writing that marketing factors require a limitation on the number of shares to be underwritten, then the

  
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Initiating Holders shall so advise all Holders of Registrable Securities that otherwise would be underwritten pursuant hereto, and the number of Registrable Securities that may be included in the
underwriting shall be allocated among such Holders of Registrable Securities, including the Initiating Holders, in proportion (as nearly as practicable) to the number of Registrable Securities owned by each Holder or in such other proportion as
shall mutually be agreed to by all such selling Holders; provided, however, that the number of Registrable Securities held by the Holders to be included in such underwriting shall not be reduced unless all other securities are first entirely
excluded from the underwriting. To facilitate the allocation of shares in accordance with the above provisions, the Company or the underwriters may round the number of shares allocated to any Holder to the nearest one hundred (100) shares. 

(b) In connection with any offering involving an underwriting of shares of the Company’s capital stock pursuant to
Subsection 2.2, the Company shall not be required to include any of the Holders’ Registrable Securities in such underwriting unless the Holders accept the terms of the underwriting as agreed upon between the Company
and its underwriters, and then only in such quantity as the underwriters in their sole discretion determine will not jeopardize the success of the offering by the Company. If the total number of securities, including Registrable Securities,
requested by stockholders to be included in such offering exceeds the number of securities to be sold (other than by the Company) that the underwriters in their reasonable discretion determine is compatible with the success of the offering, then the
Company shall be required to include in the offering only that number of such securities, including Registrable Securities, which the underwriters and the Company in their sole discretion determine will not jeopardize the success of the offering. If
the underwriters determine that less than all of the Registrable Securities requested to be registered can be included in such offering, then the Registrable Securities that are included in such offering shall be allocated among the selling Holders
in proportion (as nearly as practicable to) the number of Registrable Securities owned by each selling Holder or in such other proportions as shall mutually be agreed to by all such selling Holders. To facilitate the allocation of shares in
accordance with the above provisions, the Company or the underwriters may round the number of shares allocated to any Holder to the nearest one hundred (100) shares. Notwithstanding the foregoing, in no event shall (i) the number of
Registrable Securities included in the offering be reduced unless all other securities (other than securities to be sold by the Company) are first entirely excluded from the offering, or (ii) the number of Registrable Securities included in the
offering be reduced below thirty percent (30%) of the total number of securities included in such offering, unless such offering is the IPO, in which case the selling Holders may be excluded further if the underwriters make the determination
described above and no other stockholder’s securities are included in such offering. For purposes of the provision in this Subsection 2.3(b) concerning apportionment, for any selling Holder that is a partnership,
limited liability company, or corporation, the partners, members, retired partners, retired members, stockholders, and Affiliates of such Holder, or the estates and Immediate Family Members of any such partners, retired partners, members, and
retired members and any trusts for the benefit of any of the foregoing Persons, shall be deemed to be a single “selling Holder,” and any pro rata reduction with respect to such “selling Holder” shall be based upon the aggregate
number of Registrable Securities owned by all Persons included in such “selling Holder,” as defined in this sentence. 
 2.4
Obligations of the Company. Whenever required under this Section 2 to effect the registration of any Registrable Securities, the Company shall, as expeditiously as reasonably possible: 

  
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 (a) prepare and file with the SEC a registration statement with respect to such Registrable
Securities and use its commercially reasonable efforts to cause such registration statement to become effective and, upon the request of the Holders of a majority of the Registrable Securities registered thereunder, keep such registration statement
effective for a period of up to one hundred twenty (120) days or, if earlier, until the distribution contemplated in the registration statement has been completed; provided, however, that such one hundred twenty (120) day period
shall be extended for a period of time equal to the period the Holder refrains, at the request of an underwriter of Common Stock (or other securities) of the Company, from selling any securities included in such registration; 

(b) prepare and file with the SEC such amendments and supplements to such registration statement, and the prospectus used in connection with
such registration statement, as may be necessary to comply with the Securities Act in order to enable the disposition of all securities covered by such registration statement; 

(c) furnish to the selling Holders such numbers of copies of a prospectus, including a preliminary prospectus, as required by the Securities
Act, and such other documents as the Holders may reasonably request in order to facilitate their disposition of their Registrable Securities; 

(d) use its commercially reasonable efforts to register and qualify the securities covered by such registration statement under such other
securities or blue-sky laws of such jurisdictions as shall be reasonably requested by the selling Holders; provided that the Company shall not be required to qualify to do business or to file a general
consent to service of process in any such states or jurisdictions, unless the Company is already subject to service in such jurisdiction and except as may be required by the Securities Act; 

(e) in the event of any underwritten public offering, enter into and perform its obligations under an underwriting agreement, in usual and
customary form, with the underwriter(s) of such offering; 
 (f) use its commercially reasonable efforts to cause all such Registrable
Securities covered by such registration statement to be listed on a national securities exchange or trading system and each securities exchange and trading system (if any) on which similar securities issued by the Company are then listed; 

(g) provide a transfer agent and registrar for all Registrable Securities registered pursuant to this Agreement and provide a CUSIP number for
all such Registrable Securities, in each case not later than the effective date of such registration; 
 (h) promptly make available for
inspection by the selling Holders, any managing underwriter(s) participating in any disposition pursuant to such registration statement, and any attorney or accountant or other agent retained by any such underwriter or selected by the selling
Holders, all financial and other records, pertinent corporate documents, and properties of the Company, and cause the Company’s officers, directors, employees, and independent accountants to supply all information reasonably requested by any
such seller, underwriter, attorney, accountant, or agent, in each case, as necessary or advisable to verify the accuracy of the information in such registration statement and to conduct appropriate due diligence in connection therewith; 

  
 8 

 (i) notify each selling Holder, promptly after the Company receives notice thereof, of the
time when such registration statement has been declared effective or a supplement to any prospectus forming a part of such registration statement has been filed; and 

(j) after such registration statement becomes effective, notify each selling Holder of any request by the SEC that the Company amend or
supplement such registration statement or prospectus. 
 In addition, the Company shall ensure that, at all times after any registration
statement covering a public offering of securities of the Company under the Securities Act shall have become effective, its insider trading policy shall provide that the Company’s directors may implement a trading program under Rule 10b5-1 of the Exchange Act. 
 2.5 Furnish Information. It shall be a condition precedent to the
obligations of the Company to take any action pursuant to this Section 2 with respect to the Registrable Securities of any selling Holder that such Holder shall furnish to the Company such information regarding itself, the
Registrable Securities held by it, and the intended method of disposition of such securities as is reasonably required to effect the registration of such Holder’s Registrable Securities. 

2.6 Expenses of Registration. All expenses (other than Selling Expenses) incurred in connection with registrations, filings, or
qualifications pursuant to Section 2, including all registration, filing, and qualification fees; printers’ and accounting fees; fees and disbursements of counsel for the Company; and the reasonable fees and
disbursements, not to exceed $25,000, of one counsel for the selling Holders (“Selling Holder Counsel”), shall be borne and paid by the Company; provided, however, that the Company shall not be required to pay for any
expenses of any registration proceeding begun pursuant to Subsection 2.1 if the registration request is subsequently withdrawn at the request of the Holders of a majority of the Registrable Securities to be registered (in
which case all selling Holders shall bear such expenses pro rata based upon the number of Registrable Securities that were to be included in the withdrawn registration), unless the Holders of a majority of the Registrable Securities agree to forfeit
their right to one registration pursuant to Subsections 2.1(a) or 2.1(b), as the case may be; provided further that if, at the time of such withdrawal, the Holders shall have learned of a material adverse
change in the condition, business, or prospects of the Company from that known to the Holders at the time of their request and have withdrawn the request with reasonable promptness after learning of such information then the Holders shall not be
required to pay any of such expenses and shall not forfeit their right to one registration pursuant to Subsections 2.1(a) or 2.1(b). All Selling Expenses relating to Registrable Securities registered pursuant to this
Section 2 shall be borne and paid by the Holders pro rata on the basis of the number of Registrable Securities registered on their behalf. 

2.7 Delay of Registration. No Holder shall have any right to obtain or seek an injunction restraining or otherwise delaying any
registration pursuant to this Agreement as the result of any controversy that might arise with respect to the interpretation or implementation of this Section 2. 

  
 9 

 2.8 Indemnification. If any Registrable Securities are included in a registration
statement under this Section 2: 
 (a) To the extent permitted by law, the Company will indemnify and hold
harmless each selling Holder, and the partners, members, officers, directors, and stockholders of each such Holder; legal counsel and accountants for each such Holder; any underwriter (as defined in the Securities Act) for each such Holder; and each
Person, if any, who controls such Holder or underwriter within the meaning of the Securities Act or the Exchange Act, against any Damages, and the Company will pay to each such Holder, underwriter, controlling Person, or other aforementioned Person
any legal or other expenses reasonably incurred thereby in connection with investigating or defending any claim or proceeding from which Damages may result, as such expenses are incurred; provided, however, that the indemnity agreement
contained in this Subsection 2.8(a) shall not apply to amounts paid in settlement of any such claim or proceeding if such settlement is effected without the consent of the Company, which consent shall not be unreasonably
withheld, nor shall the Company be liable for any Damages to the extent that they arise out of or are based upon actions or omissions made in reliance upon and in conformity with written information furnished by or on behalf of any such Holder,
underwriter, controlling Person, or other aforementioned Person expressly for use in connection with such registration. 
 (b) To the extent
permitted by law, each selling Holder, severally and not jointly, will indemnify and hold harmless the Company, and each of its directors, each of its officers who has signed the registration statement, each Person (if any), who controls the Company
within the meaning of the Securities Act, legal counsel and accountants for the Company, any underwriter (as defined in the Securities Act), any other Holder selling securities in such registration statement, and any controlling Person of any such
underwriter or other Holder, against any Damages, in each case only to the extent that such Damages arise out of or are based upon actions or omissions made in reliance upon and in conformity with written information furnished by or on behalf of
such selling Holder expressly for use in connection with such registration; and each such selling Holder will pay to the Company and each other aforementioned Person any legal or other expenses reasonably incurred thereby in connection with
investigating or defending any claim or proceeding from which Damages may result, as such expenses are incurred; provided, however, that the indemnity agreement contained in this Subsection 2.8(b) shall not apply to
amounts paid in settlement of any such claim or proceeding if such settlement is effected without the consent of the Holder, which consent shall not be unreasonably withheld; and provided further that in no event shall the aggregate amounts
payable by any Holder by way of indemnity or contribution under Subsections 2.8(b) and 2.8(d) exceed the proceeds from the offering received by such Holder (net of any Selling Expenses paid by such Holder), except in
the case of fraud or willful misconduct by such Holder. 
 (c) Promptly after receipt by an indemnified party under this
Subsection 2.8 of notice of the commencement of any action (including any governmental action) for which a party may be entitled to indemnification hereunder, such indemnified party will, if a claim in respect
thereof is to be made against any indemnifying party under this Subsection 2.8, give the indemnifying party notice of the commencement thereof. The indemnifying party shall have the right to participate in such action and,
to the extent the indemnifying party so desires, participate jointly with any other indemnifying party to which notice has been given, and to assume the defense thereof with counsel mutually satisfactory to the parties; provided, however,
that an 

  
 10 

 
indemnified party (together with all other indemnified parties that may be represented without conflict by one counsel) shall have the right to retain one separate counsel, with the fees and
expenses to be paid by the indemnifying party, if representation of such indemnified party by the counsel retained by the indemnifying party would be inappropriate due to actual or potential differing interests between such indemnified party and any
other party represented by such counsel in such action. The failure to give notice to the indemnifying party within a reasonable time of the commencement of any such action shall relieve such indemnifying party of any liability to the indemnified
party under this Subsection 2.8, to the extent that such failure materially prejudices the indemnifying party’s ability to defend such action. 

(d) To provide for just and equitable contribution to joint liability under the Securities Act in any case in which either: (i) any party
otherwise entitled to indemnification hereunder makes a claim for indemnification pursuant to this Subsection 2.8 but it is judicially determined (by the entry of a final judgment or decree by a court of competent
jurisdiction and the expiration of time to appeal or the denial of the last right of appeal) that such indemnification may not be enforced in such case, notwithstanding the fact that this Subsection 2.8 provides for
indemnification in such case, or (ii) contribution under the Securities Act may be required on the part of any party hereto for which indemnification is provided under this Subsection 2.8, then, and in each such case,
such parties will contribute to the aggregate losses, claims, damages, liabilities, or expenses to which they may be subject (after contribution from others) in such proportion as is appropriate to reflect the relative fault of each of the
indemnifying party and the indemnified party in connection with the statements, omissions, or other actions that resulted in such loss, claim, damage, liability, or expense, as well as to reflect any other relevant equitable considerations. The
relative fault of the indemnifying party and of the indemnified party shall be determined by reference to, among other things, whether the untrue or allegedly untrue statement of a material fact, or the omission or alleged omission of a material
fact, relates to information supplied by the indemnifying party or by the indemnified party and the parties’ relative intent, knowledge, access to information, and opportunity to correct or prevent such statement or omission; provided,
however, that, in any such case (x) no Holder will be required to contribute any amount in excess of the public offering price of all such Registrable Securities offered and sold by such Holder pursuant to such registration statement, and
(y) no Person guilty of fraudulent misrepresentation (within the meaning of Section 11(f) of the Securities Act) will be entitled to contribution from any Person who was not guilty of such fraudulent misrepresentation; and provided
further that in no event shall a Holder’s liability pursuant to this Subsection 2.8(d), when combined with the amounts paid or payable by such Holder pursuant to Subsection 2.8(b), exceed
the proceeds from the offering received by such Holder (net of any Selling Expenses paid by such Holder), except in the case of willful misconduct or fraud by such Holder. 

(e) Notwithstanding the foregoing, to the extent that the provisions on indemnification and contribution contained in the underwriting
agreement entered into in connection with the underwritten public offering are in conflict with the foregoing provisions, the provisions in the underwriting agreement shall control. 

(f) Unless otherwise superseded by an underwriting agreement entered into in connection with the underwritten public offering, the obligations
of the Company and Holders under this Subsection 2.8 shall survive the completion of any offering of Registrable Securities in a registration under this Section 2, and otherwise shall survive the
termination of this Agreement. 

  
 11 

 2.9 Reports Under Exchange Act. With a view to making available to the Holders the
benefits of SEC Rule 144 and any other rule or regulation of the SEC that may at any time permit a Holder to sell securities of the Company to the public without registration or pursuant to a registration on Form
S-3, the Company shall: 
 (a) make and keep available adequate current public information, as those
terms are understood and defined in SEC Rule 144, at all times after the effective date of the registration statement filed by the Company for the IPO; 

(b) use commercially reasonable efforts to file with the SEC in a timely manner all reports and other documents required of the Company under
the Securities Act and the Exchange Act (at any time after the Company has become subject to such reporting requirements); and 
 (c)
furnish to any Holder, so long as the Holder owns any Registrable Securities, forthwith upon request (i) to the extent accurate, a written statement by the Company that it has complied with the reporting requirements of SEC Rule 144 (at any
time after ninety (90) days after the effective date of the registration statement filed by the Company for the IPO), the Securities Act, and the Exchange Act (at any time after the Company has become subject to such reporting requirements), or
that it qualifies as a registrant whose securities may be resold pursuant to Form S-3 (at any time after the Company so qualifies); (ii) a copy of the most recent annual or quarterly report of the Company and
such other reports and documents so filed by the Company; and (iii) such other information as may be reasonably requested in availing any Holder of any rule or regulation of the SEC that permits the selling of any such securities without
registration (at any time after the Company has become subject to the reporting requirements under the Exchange Act) or pursuant to Form S-3 (at any time after the Company so qualifies to use such form). 

2.10 Limitations on Subsequent Registration Rights. From and after the date of this Agreement, the Company shall not, without the prior
written consent of the holders of at least a majority of the shares of Common Stock issued or issuable upon conversion of the then outstanding shares of Preferred Stock held by the Investors, enter into any agreement with any holder or prospective
holder of any securities of the Company that (i) would provide to such holder the right to include securities in any registration on other than either a pro rata basis with respect to the Registrable Securities or on a subordinate basis after
all Holders have had the opportunity to include in the registration and offering all shares of Registrable Securities that they wish to so include; or (ii) allow such holder or prospective holder to initiate a demand for registration of any
securities held by such holder or prospective holder; provided that this limitation shall not apply to any additional Investor who becomes a party to this Agreement in accordance with Subsection 6.9. 

2.11 “Market Stand-off” Agreement. Each Holder hereby
agrees that it will not, without the prior written consent of the managing underwriter, during the period commencing on the date of the final prospectus relating to the IPO, and ending on the date specified by the Company and the managing
underwriter (such period not to exceed one hundred eighty (180) days, or such other period as may be requested by the Company or an underwriter to accommodate regulatory restrictions on (1) the publication or other distribution of research
reports and (2) analyst recommendations and opinions, including, but not limited to, the restrictions contained in FINRA 

  
 12 

 
Rule 2711(f)(4) or NYSE Rule 472(f)(4), or any successor provisions or amendments thereto): (i) lend; offer; pledge; sell; contract to sell; sell any option or contract to purchase; purchase any
option or contract to sell; grant any option, right, or warrant to purchase; or otherwise transfer or dispose of, directly or indirectly, any shares of Common Stock or any securities convertible into or exercisable or exchangeable (directly or
indirectly) for Common Stock (whether such shares or any such securities are then owned by the Holder or are thereafter acquired) or (ii) enter into any swap or other arrangement that transfers to another, in whole or in part, any of the
economic consequences of ownership of such securities, whether any such transaction described in clause (i) or (ii) above is to be settled by delivery of Common Stock or other securities, in cash, or otherwise. The foregoing provisions of this
Subsection 2.11 shall apply only to the IPO and shall not apply to the sale of any shares to an underwriter pursuant to an underwriting agreement, and shall be applicable to the Holders only if all officers, directors and
greater than 1% stockholders of the Company are subject to the same restrictions. Each Holder further agrees to execute such agreements as may be reasonably requested by the underwriters in connection with such registration that are consistent with
this Subsection 2.11 or that are necessary to give further effect thereto. Any discretionary waiver or termination of the restrictions of any or all of such agreements by the Company or the underwriters shall apply to all Holders
subject to such agreements pro rata based on the number of shares subject to such agreements, after giving effect to relative rights of priority in regards to “cut-backs” as set forth in this
Agreement. 
 2.12 Restrictions on Transfer. 

(a) The Preferred Stock and the Registrable Securities shall not be sold, pledged, or otherwise transferred, and the Company shall not
recognize and shall issue stop-transfer instructions to its transfer agent with respect to any such sale, pledge, or transfer, except upon the conditions specified in this Agreement, which conditions are intended to ensure compliance with the
provisions of the Securities Act. A transferring Holder will cause any proposed purchaser, pledgee, or transferee of the Preferred Stock and the Registrable Securities held by such Holder to agree to take and hold such securities subject to the
provisions and upon the conditions specified in this Agreement. 
 (b) Each certificate, instrument, or book entry representing (i) the
Preferred Stock, (ii) the Registrable Securities, and (iii) any other securities issued in respect of the securities referenced in clauses (i) and (ii), upon any stock split, stock dividend, recapitalization, merger, consolidation, or
similar event, shall (unless otherwise permitted by the provisions of Subsection 2.12(c)) be notated with a legend substantially in the following form: 

THE SECURITIES REPRESENTED HEREBY HAVE BEEN ACQUIRED FOR INVESTMENT AND HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933. SUCH SHARES
MAY NOT BE SOLD, PLEDGED, OR TRANSFERRED IN THE ABSENCE OF SUCH REGISTRATION OR A VALID EXEMPTION FROM THE REGISTRATION AND PROSPECTUS DELIVERY REQUIREMENTS OF SAID ACT. 

THE SECURITIES REPRESENTED HEREBY MAY BE TRANSFERRED ONLY IN ACCORDANCE WITH THE TERMS OF AN AGREEMENT BETWEEN THE COMPANY AND THE
STOCKHOLDER, A COPY OF WHICH IS ON FILE WITH THE SECRETARY OF THE COMPANY. 

  
 13 

 The Holders consent to the Company making a notation in its records and giving instructions
to any transfer agent of the Restricted Securities in order to implement the restrictions on transfer set forth in this Subsection 2.12. 

(c) The holder of such Restricted Securities, by acceptance of ownership thereof, agrees to comply in all respects with the provisions of this
Section 2. Before any proposed sale, pledge, or transfer of any Restricted Securities, unless there is in effect a registration statement under the Securities Act covering the proposed transaction, the Holder thereof shall
give notice to the Company of such Holder’s intention to effect such sale, pledge, or transfer. Each such notice shall describe the manner and circumstances of the proposed sale, pledge, or transfer in sufficient detail and, if reasonably
requested by the Company, shall be accompanied at such Holder’s expense by either (i) a written opinion of legal counsel who shall, and whose legal opinion shall, be reasonably satisfactory to the Company, addressed to the Company, to the
effect that the proposed transaction may be effected without registration under the Securities Act; (ii) a “no action” letter from the SEC to the effect that the proposed sale, pledge, or transfer of such Restricted Securities without
registration will not result in a recommendation by the staff of the SEC that action be taken with respect thereto; or (iii) any other evidence reasonably satisfactory to counsel to the Company to the effect that the proposed sale, pledge, or
transfer of the Restricted Securities may be effected without registration under the Securities Act, whereupon the Holder of such Restricted Securities shall be entitled to sell, pledge, or transfer such Restricted Securities in accordance with the
terms of the notice given by the Holder to the Company. The Company will not require such a legal opinion or “no action” letter (x) in any transaction in compliance with SEC Rule 144; or (y) in any transaction in which such
Holder distributes Restricted Securities to an Affiliate of such Holder for no consideration; provided that each transferee agrees in writing to be subject to the terms of this Subsection 2.12. Each certificate,
instrument, or book entry representing the Restricted Securities transferred as above provided shall be notated with, except if such transfer is made pursuant to SEC Rule 144, the appropriate restrictive legend set forth in
Subsection 2.12(b), except that such certificate instrument, or book entry shall not be notated with such restrictive legend if, in the opinion of counsel for such Holder and the Company, such legend is not required in
order to establish compliance with any provisions of the Securities Act. 
 2.13 Termination of Registration Rights. The right of any
Holder to request registration or inclusion of Registrable Securities in any registration pursuant to Subsections 2.1 or 2.2 shall terminate upon the earliest to occur of: 

(a) the closing of a Deemed Liquidation Event, as such term is defined in the Company’s Certificate of Incorporation; 

(b) such time as Rule 144 or another similar exemption under the Securities Act is available for the sale of all of such Holder’s
shares without limitation during a three-month period without registration; and 
 (c) the five year anniversary of the IPO. 

  
 14 

 3. Information and Observer Rights. 

3.1 Delivery of Financial Statements. The Company shall deliver to each Major Investor, provided that the Board of Directors has
not reasonably determined that such Major Investor is a Competitor of the Company: 
 (a) as soon as practicable, but in any event within
one hundred and eighty (180) days after the end of each fiscal year of the Company, financial statements of the Company for such year including a consolidated balance sheet of the Company as of the end of such year, and statements of income and
statements of cash flow of the Company for such year, setting forth in each case in comparative form the figures for the previous fiscal year, all in reasonable detail, United States dollar-denominated, prepared in accordance with GAAP, audited by
one of the “big four” U.S. accounting firms, which has been approved by Holders of a majority of the Registrable Securities (the “Accounting Firm”), provided that Deloitte shall be deemed to have been approved by
such Holders; 
 (b) as soon as practicable, but in any event within forty-five (45) days after
the end of each of the first three (3) quarters of each fiscal year of the Company, unaudited statements of income and cash flows for such fiscal quarter, and an unaudited balance sheet as of the end of such fiscal quarter, all prepared in
accordance with GAAP and reviewed by the Accounting Firm (except that such financial statements may (i) be subject to normal year-end audit adjustments; and (ii) not contain all notes thereto that
may be required in accordance with GAAP); 
 (c) as soon as practicable, but in any event within forty-five (45) days after the end of
each of the first three (3) quarters of each fiscal year of the Company, a statement showing the number of shares of each class and series of capital stock and securities convertible into or exercisable for shares of capital stock outstanding
at the end of the period, the Common Stock issuable upon conversion or exercise of any outstanding securities convertible or exercisable for Common Stock and the exchange ratio or exercise price applicable thereto, and the number of shares of issued
stock options and stock options not yet issued but reserved for issuance, if any, all in sufficient detail as to permit the Major Investors to calculate their respective percentage equity ownership in the Company, and certified by the chief
financial officer or chief executive officer of the Company as being true, complete, and correct; 
 (d) as soon as practicable, but in any
event within ten (10) days of the end of each month, a monthly report in a form approved by the Board of Directors; 
 (e) as soon as
practicable, but in any event thirty (30) days before the end of each fiscal year, a budget and business plan for the next fiscal year (collectively, the “Budget”), approved by the Board of Directors and prepared on a monthly
basis, including balance sheets, income statements, and statements of cash flow for such months and, promptly after prepared, any other budgets or revised budgets prepared by the Company; and 

(f) such other information relating to the financial condition, business, prospects, or corporate affairs of the Company as any Major Investor
may from time to time reasonably request; provided, however, that the Company shall not be obligated under this Subsection 3.1 to provide information (i) that the Company reasonably determines in good faith to

  
 15 

 
be a trade secret or confidential information (unless covered by an enforceable confidentiality agreement, in a form acceptable to the Company); or (ii) the disclosure of which would
adversely affect the attorney-client privilege between the Company and its counsel. 
 If, for any period, the Company has any subsidiary
whose accounts are consolidated with those of the Company, then in respect of such period the financial statements delivered pursuant to the foregoing Sections shall be the consolidated and consolidating financial statements of the Company and
all such consolidated subsidiaries. 
 Notwithstanding anything else in this Subsection 3.1 to the contrary, the
Company may cease providing the information set forth in this Subsection 3.1 during the period starting with the date thirty (30) days before the Company’s good-faith estimate of the date of filing of a
registration statement if it reasonably concludes it must do so to comply with the SEC rules applicable to such registration statement and related offering; provided that the Company’s covenants under this
Subsection 3.1 shall be reinstated at such time as the Company is no longer actively employing its commercially reasonable efforts to cause such registration statement to become effective. 

3.2 Inspection. The Company shall permit each Major Investor (provided that the Board of Directors has not reasonably determined
that such Major Investor is a Competitor of the Company), at such Major Investor’s expense, to visit and inspect the Company’s properties; examine its books of account and records; and discuss the Company’s affairs, finances, and
accounts with its officers, during normal business hours of the Company as may be reasonably requested by the Major Investor; provided, however, that the Company shall not be obligated pursuant to this Subsection 3.2
to provide access to any information that it reasonably and in good faith considers to be a trade secret or confidential information (unless covered by an enforceable confidentiality agreement, in form acceptable to the Company) or the disclosure of
which would adversely affect the attorney-client privilege between the Company and its counsel. 
 3.3 Observer. For so long as Arkin
Bio Ventures Limited Partnership (“Arkin”), together with its Affiliates, continue to own beneficially at least 100,000 shares of Common Stock of the Company (including shares of Common Stock issued or issuable upon conversion of
Preferred Stock), Arkin shall be entitled to designate one (1) observer to the Board of Directors (the “Observer”), who shall be entitled to attend any meeting of the Board of Directors, but shall not be entitled to vote in
such meetings; provided, however, that such appointment of the Observer is conditional upon the Observer entering into a confidentiality agreement with the Company in a form acceptable to Company. 

The rights of the Observer shall be subject to the following: 

(a) The Company shall give the Observer the same prior notice given to the members of the Board of Directors regarding any proposed meeting of
the Board of Directors or of any committee of the Board of Directors, such notice in all cases to include true and complete copies of all documents furnished to any member of the Board of Directors in connection with such meeting. The Observer will
be entitled to be present in person as an observer at any such meeting or, if a meeting is held by telephone conference, to participate therein for the purpose of listening thereto. 

  
 16 

 (b) The Company will deliver to each Observer copies of all papers which may be distributed
from time to time to the Directors at such time as such papers are so distributed to them, including copies of any written consent. 
 (c)
The Observer will treat and maintain such information in strict confidence, and will not disclose such information without the prior written consent of the Company. 

(d) If the Board of Directors determines, in good faith, that the attendance of the person appointed as the Observer in a specific meeting (or
part of the specific meeting) (i) constitutes a conflict of interests between such person (or his designator) and the Company, (ii) would adversely impact the attorney/client privilege, or (iii) would result in disclosure of trade
secrets, or if such person is affiliated with a direct competitor of the Company, then the Board may exclude such person from attending such specific meeting (or relevant part thereof), accordingly, any related materials may as well be withheld from
the such person, provided that all Board observers are afforded equivalent treatment. 
 3.4 Termination of Information and
Observer Rights. The covenants set forth in Subsection 3.1, Subsection 3.2 and Subsection 3.3 shall terminate and be of no further force or effect (a) immediately
before the consummation of the IPO, (b) when the Company first becomes subject to the periodic reporting requirements of Section 13 or 15(d) of the Exchange Act, or (c) upon a Deemed Liquidation Event, as such term is defined
in the Company’s Certificate of Incorporation, whichever event occurs first. 
 3.5 Confidentiality. Each Investor agrees that
such Investor will keep confidential and will not disclose, divulge, or use for any purpose (other than to monitor its investment in the Company) any confidential information obtained from the Company pursuant to the terms of this Agreement
(including notice of the Company’s intention to file a registration statement), unless such confidential information (a) is known or becomes known to the public in general (other than as a result of a breach of this
Subsection 3.5 by such Investor), (b) is or has been independently developed or conceived by the Investor without use of the Company’s confidential information, or (c) is or has been made known or disclosed to the
Investor by a third party without a breach of any obligation of confidentiality such third party may have to the Company; provided, however, that an Investor may disclose confidential information (i) to its attorneys, accountants,
consultants, and other professionals to the extent necessary to obtain their services in connection with monitoring its investment in the Company; (ii) to any prospective purchaser of any Registrable Securities from such Investor, if such
prospective purchaser agrees to be bound by the provisions of this Subsection 3.5; (iii) to any Affiliate, partner, member, stockholder, or wholly owned subsidiary of such Investor in the ordinary course of business,
provided that such Investor informs such Person that such information is confidential and directs such Person to maintain the confidentiality of such information; or (iv) as may otherwise be required by law, provided that the
Investor promptly notifies the Company of such disclosure and takes reasonable steps to minimize the extent of any such required disclosure. 
 4.
Rights to Future Stock Issuances. 
 4.1 Right of First Offer. Subject to the terms and conditions of this
Subsection 4.1 and applicable securities laws, if the Company proposes to offer or sell any New Securities, the 

  
 17 

 
Company shall first offer such New Securities to each Investor. An Investor shall be entitled to apportion the right of first offer hereby granted to it in such proportions as it deems
appropriate, among (i) itself, (ii) its Affiliates and (iii) its beneficial interest holders, such as limited partners, members or any other Person having “beneficial ownership,” as such term is defined in Rule 13d-3 promulgated under the Exchange Act, of such Investor (“Investor Beneficial Owners”); provided that each such Affiliate or Investor Beneficial Owner (x) is not a Competitor of the
Company, unless such party’s purchase of New Securities is otherwise consented to by the Board of Directors, (y) agrees to enter into this Agreement, the Voting Agreement and the Right of First Refusal and
Co-Sale Agreement of even date herewith among the Company, the Investors and the other parties named therein, as an “Investor” under each such agreement (provided that any Competitor of
the Company shall not be entitled to any rights as an Investor under Subsections 3.1, 3.2, 3.3 and 4.1 hereof), and (z) agrees to purchase at least such number of New Securities as are allocable
hereunder to the Investor holding the fewest number of Preferred Stock and any other Derivative Securities. 
 (a) The Company shall give
notice (the “Offer Notice”) to each Investor, stating (i) its bona fide intention to offer such New Securities, (ii) the number of such New Securities to be offered, and (iii) the price and terms, if any, upon which
it proposes to offer such New Securities. 
 (b) By notification to the Company within twenty (20) days after the Offer Notice is
given, each Investor may elect to purchase or otherwise acquire, at the price and on the terms specified in the Offer Notice, up to that portion of such New Securities which equals the proportion that the Common Stock then held by such Investor
(including all shares of Common Stock then issuable (directly or indirectly) upon conversion and/or exercise, as applicable, of the Preferred Stock and any other Derivative Securities then held by such Investor) bears to the total Common Stock of
the Company then outstanding (assuming full conversion and/or exercise, as applicable, of all Preferred Stock and other Derivative Securities). At the expiration of such twenty (20) day period, the Company shall promptly notify each Investor
that elects to purchase or acquire all the shares available to it (each, a “Fully Exercising Investor”) of any other Investor’s failure to do likewise. During the ten (10) day period commencing after the Company has given
such notice, each Fully Exercising Investor may, by giving notice to the Company, elect to purchase or acquire, in addition to the number of shares specified above, up to that portion of the New Securities for which Investors were entitled to
subscribe but that were not subscribed for by the Investors which is equal to the proportion that the Common Stock issued and held, or issuable (directly or indirectly) upon conversion and/or exercise, as applicable, of Preferred Stock and any other
Derivative Securities then held, by such Fully Exercising Investor bears to the Common Stock issued and held, or issuable (directly or indirectly) upon conversion and/or exercise, as applicable, of the Preferred Stock and any other Derivative
Securities then held, by all Fully Exercising Investors who wish to purchase such unsubscribed shares. The closing of any sale pursuant to this Subsection 4.1(b) shall occur within the later of ninety (90) days
of the date that the Offer Notice is given and the date of initial sale of New Securities pursuant to Subsection 4.1(c). 
 (c)
If all New Securities referred to in the Offer Notice are not elected to be purchased or acquired as provided in Subsection 4.1(b), the Company may, during the ninety (90) day period following the expiration of the
periods provided in Subsection 4.1(b), offer and sell the 

  
 18 

 
remaining unsubscribed portion of such New Securities to any Person or Persons at a price not less than, and upon terms no more favorable to the offeree than, those specified in the Offer Notice.
If the Company does not enter into an agreement for the sale of the New Securities within such period, or if such agreement is not consummated within thirty (30) days of the execution thereof, the right provided hereunder shall be deemed to be
revived and such New Securities shall not be offered unless first reoffered to the Investors in accordance with this Subsection 4.1. 

(d) The right of first offer in this Subsection 4.1 shall not be applicable to (i) Exempted Securities (as
defined in the Company’s Certificate of Incorporation); (ii) shares of Common Stock issued in the IPO; and (iii) the issuance of shares of Series C Preferred Stock pursuant to the Purchase Agreement. 

4.2 Termination. The covenants set forth in Subsection 4.1 shall terminate and be of no further force or
effect (i) immediately before the consummation of the IPO or (ii) upon a Deemed Liquidation Event, as such term is defined in the Company’s Certificate of Incorporation, whichever event occurs first. 

5. Additional Covenants. 

5.1 Insurance. The Company shall use its commercially reasonable efforts to obtain, within ninety (90) days of the date hereof,
from financially sound and reputable insurers Directors and Officers liability insurance in an amount and on terms and conditions satisfactory to the Board of Directors, including the Series C At-Large
Director (as defined in the Voting Agreement) then serving, if any, and will use commercially reasonable efforts to cause such insurance policies to be maintained until such time as the Board of Directors, including the Series C At-Large Director then serving, if any, determines that such insurance should be discontinued. 
 5.2
Employee Agreements. The Company will cause (i) each person now or hereafter employed by it or by any subsidiary (or engaged by the Company or any subsidiary as a consultant/independent contractor) with access to confidential information
and/or trade secrets to enter into a nondisclosure and proprietary rights assignment agreement; and (ii) each Key Employee to enter into a one (1) year nonsolicitation agreement. In addition, the Company shall not amend, modify, terminate,
waive, or otherwise alter, in whole or in part, any of the above-referenced agreements or any restricted stock agreement between the Company and any employee, without the consent of the Board of Directors. 

5.3 Employee Stock. Unless otherwise approved by the Board of Directors, all future employees and consultants of the Company who
purchase, receive options to purchase, or receive awards of shares of the Company’s capital stock after the date hereof shall be required to execute restricted stock or option agreements, as applicable, providing for (i) vesting of shares
over a four (4) year period, with the first twenty-five percent (25%) of such shares vesting following twelve (12) months of continued employment or service, and the remaining shares vesting in equal installments over the following thirty-six (36) months, and (ii) a market stand-off provision substantially similar to that in Subsection 2.11. In addition, unless otherwise approved by
the Board of Directors, the Company shall retain a “right of first refusal” on employee transfers until the Company’s IPO and shall have the right to repurchase unvested shares at cost upon termination of employment of a holder
of restricted stock. 

  
 19 

 5.4 Matters Requiring Investor Director Approval. So long as the holders of Preferred
Stock are entitled to elect a Preferred Director, the Company hereby covenants and agrees with each of the Investors that it shall not, without approval of the Board of Directors, which approval must include a majority of the following directors, if
still seated, of the PIF Director, the Arkin Director, the Global Health Director, the Series C At-Large Director, and at least one Pontifax Director (each as defined in the Voting Agreement) hire, terminate,
or change the compensation of the Chief Executive Officer, including approving any option grants or stock awards to the Chief Executive Officer. 

5.5 Board Matters. Unless otherwise determined by the vote of a majority of the directors then in office, the Board of Directors shall
meet at least quarterly in accordance with an agreed-upon schedule. The Company shall reimburse the nonemployee directors for all reasonable out-of-pocket travel
expenses incurred (consistent with the Company’s travel policy) in connection with attending meetings of the Board of Directors. The Series C At-Large Director shall be entitled in such person’s
discretion to be a member of (i) any committee of the Board of Directors and (ii) the Board of Directors of any subsidiary of the Company and any committees thereof. 

5.6 Successor Indemnification. If the Company or any of its successors or assignees consolidates with or merges into any other Person
and is not the continuing or surviving corporation or entity of such consolidation or merger, then to the extent necessary, proper provision shall be made so that the successors and assignees of the Company assume the obligations of the Company with
respect to indemnification of members of the Board of Directors as in effect immediately before such transaction, whether such obligations are contained in the Company’s Bylaws, its Certificate of Incorporation, or elsewhere, as the case may
be. 
 5.7 Indemnification Matters. The Company hereby acknowledges that one (1) or more of the directors nominated to serve on
the Board of Directors by the Investors (each a “Fund Director”) may have certain rights to indemnification, advancement of expenses and/or insurance provided by one or more of the Investors and certain of their affiliates
(collectively, the “Fund Indemnitors”). The Company hereby agrees (a) that it is the indemnitor of first resort (i.e., its obligations to any such Fund Director are primary and any obligation of the Fund Indemnitors to
advance expenses or to provide indemnification for the same expenses or liabilities incurred by such Fund Director are secondary), (b) that it shall be required to advance the full amount of expenses incurred by such Fund Director and shall be
liable for the full amount of all expenses, judgments, penalties, fines and amounts paid in settlement by or on behalf of any such Fund Director to the extent legally permitted and as required by the Company’s Certificate of Incorporation or
Bylaws of the Company (or any agreement between the Company and such Fund Director), without regard to any rights such Fund Director may have against the Fund Indemnitors, and, (c) that it irrevocably waives, relinquishes and releases the Fund
Indemnitors from any and all claims against the Fund Indemnitors for contribution, subrogation or any other recovery of any kind in respect thereof. The Company further agrees that no advancement or payment by the Fund Indemnitors on behalf of any
such Fund Director with respect to any claim for which such Fund Director has sought indemnification from the Company shall affect the foregoing and the Fund Indemnitors shall have a right of contribution and/or be subrogated to the extent of such
advancement or payment to all of the rights of recovery of such Fund Director against the Company. 

  
 20 

 5.8 United States Real Property Holding Company. The Company shall notify the
Investors promptly following any “determination date” (as defined in Treasury Regulations section 1.897-2(c)(1)) or otherwise within five (5) business days of becoming aware that the Company is,
or is reasonably likely to be, a “United States real property holding corporation” within the meaning of Section 897(c)(2) of the Code. In addition, at any time upon an Investor’s request, the Company shall issue a statement to
such Investor, in form and substance as described in Treasury Regulations sections 1.897-2(h)(1) and 1.1445-2(c) (or any successor regulations) and signed under
penalties of perjury, regarding whether any interest in the Company constitutes a “U.S. real property interest” within the meaning of Section 897(c) of the Code, together with an executed notice to the IRS described in Treasury
Regulations section 1.897-2(h)(2) (or any successor regulation). Such statement shall be delivered within ten (10) days of such Investor’s written request therefor. 

5.9 Termination of Covenants. The covenants set forth in this Section 5, except for Subsections 5.6 and
5.7, shall terminate and be of no further force or effect (a) immediately before the consummation of the IPO, (b) when the Company first becomes subject to the periodic reporting requirements of Section 12(g) or 15(d) of the
Exchange Act, or (c) upon a Deemed Liquidation Event, as such term is defined in the Company’s Certificate of Incorporation, whichever event occurs first. 

6. Miscellaneous. 
 6.1
Successors and Assigns. The rights under this Agreement may be assigned (but only with all related obligations) by a Holder to a transferee of Registrable Securities that (i) is an Affiliate of a Holder; (ii) is a
Holder’s Immediate Family Member or trust for the benefit of an individual Holder or one or more of such Holder’s Immediate Family Members; or (iii) after such transfer, holds at least 100,000 shares of Registrable Securities (subject
to appropriate adjustment for stock splits, stock dividends, combinations, and other recapitalizations); provided, however, that (x) the Company is, within a reasonable time after such transfer, furnished with written notice of the name
and address of such transferee and the Registrable Securities with respect to which such rights are being transferred; and (y) such transferee agrees in a written instrument delivered to the Company to be bound by and subject to the terms and
conditions of this Agreement, including the provisions of Subsection 2.11. For the purposes of determining the number of shares of Registrable Securities held by a transferee, the holdings of a transferee (1) that is an Affiliate or
stockholder of a Holder; (2) who is a Holder’s Immediate Family Member; or (3) that is a trust for the benefit of an individual Holder or such Holder’s Immediate Family Member shall be aggregated together and with those of the
transferring Holder; provided further that all transferees who would not qualify individually for assignment of rights shall have a single attorney-in-fact for
the purpose of exercising any rights, receiving notices, or taking any action under this Agreement. The terms and conditions of this Agreement inure to the benefit of and are binding upon the respective successors and permitted assignees of the
parties. Nothing in this Agreement, express or implied, is intended to confer upon any party other than the parties hereto or their respective successors and permitted assignees any rights, remedies, obligations or liabilities under or by reason of
this Agreement, except as expressly provided herein. 
 6.2 Governing Law. This Agreement shall be governed by the internal law of
the State of Delaware. 

  
 21 

 6.3 Counterparts. This Agreement may be executed in two (2) or more
counterparts, each of which shall be deemed an original, but all of which together shall constitute one and the same instrument. Counterparts may be delivered via facsimile, electronic mail (including pdf or any electronic signature complying with
the U.S. federal ESIGN Act of 2000, e.g., www.docusign.com) or other transmission method and any counterpart so delivered shall be deemed to have been duly and validly delivered and be valid and effective for all purposes. 

6.4 Titles and Subtitles. The titles and subtitles used in this Agreement are for convenience only and are not to be considered in
construing or interpreting this Agreement. 
 6.5 Notices. All notices and other communications given or made pursuant to this
Agreement shall be in writing and shall be deemed effectively given upon the earlier of actual receipt or (a) personal delivery to the party to be notified; (b) when sent, if sent by electronic mail or facsimile during the recipient’s
normal business hours, and if not sent during normal business hours, then on the recipient’s next business day; (c) five (5) days after having been sent by registered or certified mail, return receipt requested, postage prepaid; or
(iv) two (2) business days after the deposit with an internationally recognized overnight courier, freight prepaid, specifying next-day delivery, with written verification of receipt. All communications
shall be sent to the respective parties at their addresses as set forth on Schedule A hereto, or to the principal office of the Company and to the attention of the Chief Executive Officer, in the case of the Company, or to such email address,
facsimile number, or address as subsequently modified by written notice given in accordance with this Subsection 6.5. If notice is given to the Company, a copy shall also be sent to Cooley LLP, 500 Boylston Street, 14th Floor, Boston, MA 02116, Attention: Ryan Sansom. 
 6.6 Amendments and Waivers.
Any term of this Agreement may be amended and the observance of any term of this Agreement may be waived (either generally or in a particular instance, and either retroactively or prospectively) only with the written consent of the Company and the
holders of at least a majority of the shares of Common Stock issued or issuable upon conversion of the then outstanding shares of Preferred Stock held by the Investors; provided that the Company may in its sole discretion waive compliance
with Subsection 2.12(c) (and the Company’s failure to object promptly in writing after notification of a proposed assignment allegedly in violation of Subsection 2.12(c) shall be deemed to be a waiver); and provided further that
any provision hereof may be waived by any waiving party on such party’s own behalf, without the consent of any other party. Notwithstanding the foregoing, (i) this Agreement may not be amended or terminated and the observance of any term
hereof may not be waived with respect to any Investor without the written consent of such Investor, unless such amendment, termination, or waiver applies to all Investors in the same fashion and (ii) in the event any Major Investor whose vote
was required to effect a waiver of Section 4 purchases any New Securities in any issuance of New Securities by the Company following a waiver of Section 4, then each Major Investor shall be permitted to participate in such offering on a
pro rata basis, where the pro rata basis for such Major Investor is equal to the largest pro rata share purchased by any Major Investor who waiver and then purchased equity securities in the transaction, in accordance with the other provisions
(including notice and election periods) set forth in Section 4; provided further that this participation amount shall in no event exceed the amounts such Major Investor would be entitled to purchase pursuant to Section 4 above
notwithstanding any such waiver. The Company shall give prompt notice of any amendment or termination hereof or waiver hereunder to any party hereto 

  
 22 

 
that did not consent in writing to such amendment, termination, or waiver. Any amendment, termination, or waiver effected in accordance with this Subsection 6.6 shall be binding on all parties
hereto, regardless of whether any such party has consented thereto. No waivers of or exceptions to any term, condition, or provision of this Agreement, in any one or more instances, shall be deemed to be or construed as a further or continuing
waiver of any such term, condition, or provision. 
 6.7 Severability. In case any one or more of the provisions contained in this
Agreement is for any reason held to be invalid, illegal or unenforceable in any respect, such invalidity, illegality, or unenforceability shall not affect any other provision of this Agreement, and such invalid, illegal, or unenforceable provision
shall be reformed and construed so that it will be valid, legal, and enforceable to the maximum extent permitted by law. 
 6.8
Aggregation of Stock. All shares of Registrable Securities held or acquired by Affiliates shall be aggregated together for the purpose of determining the availability of any rights under this Agreement and such Affiliated persons may
apportion such rights as among themselves in any manner they deem appropriate. 
 6.9 Additional Investors. Notwithstanding anything
to the contrary contained herein, if the Company issues additional shares of the Company’s Preferred Stock after the date hereof, any purchaser of such shares of Preferred Stock may become a party to this Agreement by executing and delivering
an additional counterpart signature page to this Agreement, and thereafter shall be deemed an “Investor” for all purposes hereunder. No action or consent by the Investors shall be required for such joinder to this Agreement by such
additional Investor, so long as such additional Investor has agreed in writing to be bound by all of the obligations as an “Investor” hereunder. 

6.10 Entire Agreement. This Agreement (including any Schedules and Exhibits hereto) constitutes the full and entire understanding and
agreement among the parties with respect to the subject matter hereof, and any other written or oral agreement relating to the subject matter hereof existing between the parties is expressly canceled. Upon the effectiveness of this Agreement, the
Prior Agreement shall be deemed amended and restated and superseded and replaced in its entirety by this Agreement, and shall be of no further force or effect. 

6.11 Dispute Resolution. The parties (a) hereby irrevocably and unconditionally submit to the jurisdiction of the state courts of
Delaware and to the jurisdiction of the United States District Court for the District of Delaware for the purpose of any suit, action or other proceeding arising out of or based upon this Agreement, (b) agree not to commence any suit, action or
other proceeding arising out of or based upon this Agreement except in the state courts of Delaware or the United States District Court for the District of Delaware, and (c) hereby waive, and agree not to assert, by way of motion, as a
defense, or otherwise, in any such suit, action or proceeding, any claim that it is not subject personally to the jurisdiction of the above-named courts, that its property is exempt or immune from attachment or execution, that the suit, action or
proceeding is brought in an inconvenient forum, that the venue of the suit, action or proceeding is improper or that this Agreement or the subject matter hereof may not be enforced in or by such court. 

6.12 Delays or Omissions. No delay or omission to exercise any right, power, or remedy accruing to any party under this Agreement, upon
any breach or default of any other party under 

  
 23 

 
this Agreement, shall impair any such right, power, or remedy of such nonbreaching or nondefaulting party, nor shall it be construed to be a waiver of or acquiescence to any such breach or
default, or to any similar breach or default thereafter occurring, nor shall any waiver of any single breach or default be deemed a waiver of any other breach or default theretofore or thereafter occurring. All remedies, whether under this Agreement
or by law or otherwise afforded to any party, shall be cumulative and not alternative. 
 [Remainder of Page Intentionally Left Blank] 

 

  
 24 

 IN WITNESS WHEREOF, the parties have executed this Agreement as of the date first written
above. 
  

			
	COMPANY:
		
	By:	 	 /s/ Jasbir Seehra

	Name: Jasbir S. Seehra
	Title: Chief Executive Officer
	
	 Address:

	 99 Hayden Ave.

	 Building E, Suite 120

	 Lexington, MA 02421

  
 SIGNATURE
PAGE TO KEROS THERAPEUTICS, INC. AMENDED AND RESTATED INVESTORS’ RIGHTS
AGREEMENT 

 
			
	 INVESTORS:

	 PONTIFAX (ISRAEL) IV, L.P.

		
	By:	 	 /s/ Tomer Kariv

	Name: Tomer Kariv
	 Title: CEO

	
	PONTIFAX (CAYMAN) IV, L.P.
		
	By:	 	 /s/ Tomer Kariv

	Name: Tomer Kariv
	 Title: CEO

	
	PONTIFAX (CHINA) IV, L.P.
		
	By:	 	 /s/ Tomer Kariv

	Name: Tomer Kariv
	 Title: CEO

  
 SIGNATURE
PAGE TO KEROS THERAPEUTICS, INC. AMENDED AND RESTATED INVESTORS’ RIGHTS
AGREEMENT 

 
			
	 INVESTORS:

	 ARKIN BIO VENTURES LIMITED PARTNERSHIP

BY ITS GENERAL PARTNER: ARKIN BIO VENTURE PARTNERS LTD.

		
	By:	 	 /s/ Moshe Arkin

	Name: Moshe Arkin
	 Title: Director

  
 SIGNATURE
PAGE TO KEROS THERAPEUTICS, INC. AMENDED AND RESTATED INVESTORS’ RIGHTS
AGREEMENT 

 
			
	 INVESTORS:

	 PARTNERS INNOVATION FUND, LLC

		
	By:	 	 /s/ Julius Knowles

	Name: Julius Knowles
	Title: Partner
	
	 PARTNERS INNOVATION FUND II, L.P.

	
	 By: Partners Innovation II, LLC

	 Its General Partner

		
	By:	 	 /s/ Julius Knowles

	 Name: Julius Knowles

	 Title: Partner

  
 SIGNATURE
PAGE TO KEROS THERAPEUTICS, INC. AMENDED AND RESTATED INVESTORS’ RIGHTS
AGREEMENT 

 
			
	INVESTORS:
	MEDISON VENTURES LTD.
		
	By:	 	 /s/ Gil Gurfinkel

	Name: Gil Gurfinkel
	Title: Managing Partner

  
 SIGNATURE
PAGE TO KEROS THERAPEUTICS, INC. AMENDED AND RESTATED INVESTORS’ RIGHTS
AGREEMENT 

 
			
	 INVESTORS:

	 GLOBAL HEALTH SCIENCE FUND II, L.P.

	
	Signed for and on behalf of GHS Partners Limited, acting as the general partner of GHS Partnership II L.P. being the general partner of Global Health Science Fund II, L.P.
		
	By:	 	 /s/ Karimah Es Sabar

	 Name: Karimah Es Sabar

	 Title: Director

  
 SIGNATURE
PAGE TO KEROS THERAPEUTICS, INC. AMENDED AND RESTATED INVESTORS’ RIGHTS
AGREEMENT 

 
			
	INVESTORS:
	PONTIFAX LATE STAGE FUND L.P.
		
	By:	 	 /s/ Asaf Shinar

	Name: Asaf Shinar
	Title: CFO

  
 SIGNATURE
PAGE TO KEROS THERAPEUTICS, INC. AMENDED AND RESTATED INVESTORS’ RIGHTS
AGREEMENT 

 
			
	INVESTORS:
	FORESITE CAPITAL FUND IV, L.P.
	 By: Foresite Capital Management IV, LLC

its General Partner

		
	 By:
	 	 /s/ Dennis Ryan

	Name: Dennis Ryan
	Title: Chief Financial Officer
	
	Address: 600 Montgomery Street
	Suite 4500
	San Francisco, CA 94111
	Attn: Dennis Ryan
	Email: [***]

  
 SIGNATURE
PAGE TO KEROS THERAPEUTICS, INC. AMENDED AND RESTATED INVESTORS’ RIGHTS
AGREEMENT 

 
			
	INVESTORS:
	JASBIR SEEHRA
		
	 By:
	 	 /s/ Jasbir Seehra

  
 SIGNATURE
PAGE TO KEROS THERAPEUTICS, INC. AMENDED AND RESTATED INVESTORS’ RIGHTS
AGREEMENT 

 
			
	INVESTORS:
	GC&H INVESTMENTS, LLC
		
	 By:
	 	 /s/ Jim Kindler ipo

	Name: Jim Kindler
	Title: Manager

  
 SIGNATURE
PAGE TO KEROS THERAPEUTICS, INC. AMENDED AND RESTATED INVESTORS’ RIGHTS
AGREEMENT 

 
			
	INVESTORS:
	LEERINK PARTNERS CO-INVESTMENT FUND, LLC
		
	 By:
	 	 /s/ Jeffrey A. Leerink

	Name: Jeffrey A. Leerink
	Title: Manager

  
 SIGNATURE
PAGE TO KEROS THERAPEUTICS, INC. AMENDED AND RESTATED INVESTORS’ RIGHTS
AGREEMENT 

 
			
	INVESTORS:
	COWEN HEALTHCARE INVESTMENTS II LP
	By: Cowen Healthcare Investments II GP LLC its General Partner
		
	 By:
	 	 /s/ Kevin Raidy

	Name: Kevin Raidy
	Title: Managing Partner
	
	CHI EF II LP
	By: Cowen Healthcare Investments II GP LLC its General Partner
		
	 By:
	 	 /s/ Kevin Raidy

	Name: Kevin Raidy
	Title: Managing Partner

  
 SIGNATURE
PAGE TO KEROS THERAPEUTICS, INC. AMENDED AND RESTATED INVESTORS’ RIGHTS
AGREEMENT 

 
			
	ORBIMED PRIVATE INVESTENTS VII, LP
	By: OrbiMed Capital GP VII LLC
	its General Partner
	
	By: OrbiMed Advisors LLC
	its Managing Member
		
	By:	 	 /s/ Carl Gordon

	Name: Carl Gordon
	Title: Member

  
 SIGNATURE
PAGE TO KEROS THERAPEUTICS, INC. AMENDED AND RESTATED INVESTORS’ RIGHTS
AGREEMENT 

 
			
	ORBIMED GENESIS MASTER FUND, L.P.
	By: OrbiMed Genesis GP LLC
	its General Partner
	
	By: OrbiMed Advisors LLC
	its Managing Member
		
	By:	 	 /s/ Carl Gordon

	Name: Carl Gordon
	Title: Member

  
 SIGNATURE
PAGE TO KEROS THERAPEUTICS, INC. AMENDED AND RESTATED INVESTORS’ RIGHTS
AGREEMENT 

 
			
	THE BIOTECH GROWTH TRUST PLC
	By: OrbiMed Capital LLC, solely in its capacity as Portfolio Manager
		
	By:	 	 /s/ Carl Gordon

	Name: Carl Gordon
	Title: Member

  
 SIGNATURE
PAGE TO KEROS THERAPEUTICS, INC. AMENDED AND RESTATED INVESTORS’ RIGHTS
AGREEMENT 

 
			
	VENROCK HEALTHCARE CAPITAL PARTNERS III, L.P.
	By: VHCP Management III, LLC
	Its: General Partner
	
	VHCP CO-INVESTMENT HOLDINGS III, L.P.
	By: VHCP Management III, LLC
	Its: Manager
		
	By:	 	 /s/ Lisa Harris

	Name: Lisa Harris
	Title: Authorized Signatory

  
 SIGNATURE
PAGE TO KEROS THERAPEUTICS, INC. AMENDED AND RESTATED INVESTORS’ RIGHTS
AGREEMENT 

 SCHEDULE A 

Investors 
  

	
	 Pontifax (Israel) IV, L.P.

	
	 Pontifax (Cayman) IV, L.P.

	
	 Pontifax (China) IV, L.P.

	
	 Pontifax Late Stage Fund L.P.

	
	 Arkin Bio Ventures Limited Partnership

	
	 Partners Innovation Fund, LLC

	
	 Partners Innovation Fund II, L.P.

	
	 Medison Ventures Ltd.

	
	 Global Health Science Fund II, L.P.

	
	 Foresite Capital Fund IV, L.P.

	
	 OrbiMed Private Investments VII, LP

	
	 The Biotech Growth Trust PLC

	
	 OrbiMed Genesis Master Fund, LP

	
	 Leerink Partners Co-Investment Fund,
LLC

	
	 Cowen Healthcare Investments II LP

	
	 CHI EF II LP

	
	 Venrock Healthcare Capital Partners III, L.P.

	
	 VHCP Co-Investment Holdings III, LLC

	
	 GC&H Investments, LLC

	
	 Jasbir SeehraEX-10.2

 Exhibit 10.2 

KEROS THERAPEUTICS, INC. 
 2017
STOCK INCENTIVE PLAN 
 1. Purpose 

The purpose of this 2017 Stock Incentive Plan (the “Plan”) of Keros Therapeutics, Inc., a Delaware corporation (the
“Company”), is to advance the interests of the Company’s stockholders by enhancing the Company’s ability to attract, retain and motivate persons who are expected to make important contributions to the Company and by providing
such persons with equity ownership opportunities and performance-based incentives that are intended to better align the interests of such persons with those of the Company’s stockholders. Except where the context otherwise requires, the term
“Company” shall include any of the Company’s present or future parent or subsidiary corporations as defined in Sections 424(e) or (f) of the Internal Revenue Code of 1986, as amended, and any regulations promulgated thereunder
(the “Code”) and any other business venture (including, without limitation, joint venture or limited liability company) in which the Company has a controlling interest, as determined by the Board of Directors of the Company (the
“Board”). 
 2. Eligibility 

All of the Company’s employees, officers, directors, consultants and advisors are eligible to be granted options, restricted stock,
restricted stock units (“RSUs”) and other stock-based awards (each, an “Award”) under the Plan. Each person who receives an Award under the Plan is deemed a “Participant”. 

3. Administration and Delegation 
 (a)
Administration by Board of Directors. The Plan will be administered by the Board. The Board shall have authority to grant Awards and to adopt, amend and repeal such administrative rules, guidelines and practices relating to the Plan as it
shall deem advisable. The Board may construe and interpret the terms of the Plan and any Award agreements entered into under the Plan. The Board may correct any defect, supply any omission or reconcile any inconsistency in the Plan or any Award in
the manner and to the extent it shall deem expedient to carry the Plan into effect and it shall be the sole and final judge of such expediency. All decisions by the Board shall be made in the Board’s sole discretion and shall be final and
binding on all persons having or claiming any interest in the Plan or in any Award. No director or person acting pursuant to the authority delegated by the Board shall be liable for any action or determination relating to or under the Plan made in
good faith. 
 (b) Appointment of Committees. To the extent permitted by applicable law, the Board may delegate any or all of its
powers under the Plan to one or more committees or subcommittees of the Board (a “Committee”). All references in the Plan to the “Board” shall mean the Board or a Committee of the Board or the officers referred to in
Section 3(c) to the extent that the Board’s powers or authority under the Plan have been delegated to such Committee or officers. 

  
 1. 

 (c) Delegation to Officers. To the extent permitted by applicable law, the Board may
delegate to one or more officers of the Company the power to grant Awards (subject to any limitations under the Plan) to employees or officers of the Company or any of its present or future subsidiary corporations and to exercise such other powers
under the Plan as the Board may determine, provided that the Board shall fix the terms of the Awards to be granted by such officers (including the exercise price of such Awards, which may include a formula by which the exercise price will be
determined) and the maximum number of shares subject to Awards that the officers may grant; provided further, however, that no officer shall be authorized to grant Awards to any “executive officer” of the Company (as defined by Rule 3b-7 under the Securities Exchange Act of 1934, as amended (the “Exchange Act”)) or to any “officer” of the Company (as defined by Rule 16a-1 under the
Exchange Act). 
 4. Stock Available for Awards. 

(a) Number of Shares. Subject to adjustment under Section 8, Awards may be made under the Plan for up to 518,11011 shares of common stock, $0.0001 par value per share, of the Company (the “Common Stock”). If any Award expires or is terminated, surrendered or canceled without having been fully exercised,
is forfeited in whole or in part (including as the result of shares of Common Stock subject to such Award being repurchased by the Company at the original issuance price pursuant to a contractual repurchase right), or results in any Common Stock not
being issued, the unused Common Stock covered by such Award shall again be available for the grant of Awards under the Plan. Further, shares of Common Stock tendered to the Company by a Participant to exercise an Award shall be added to the number
of shares of Common Stock available for the grant of Awards under the Plan. However, in the case of Incentive Stock Options (as hereinafter defined), the foregoing provisions shall be subject to any limitations under the Code. Shares issued under
the Plan may consist in whole or in part of authorized but unissued shares or treasury shares. At no time while there is any Option (as defined below) outstanding and held by a Participant who was a resident of the State of California on the date of
grant of such Option, shall the total number of shares of Common Stock issuable upon exercise of all outstanding options and the total number of shares provided for under any stock bonus or similar plan or agreement of the Company exceed the
applicable percentage as calculated in accordance with the conditions and exclusions of Section 260.140.45 of the California Code of Regulations (the “California Regulations”), based on the shares of the Company which are outstanding
at the time the calculation is made. 
  
  

	1	 Increased by 982,533 shares, from 518,110 shares to 1,500,643 shares, pursuant to Board action taken on
December 18, 2017. 

 Increased by 442,000 shares, from 1,500,643 shares to 1,942,643 shares, pursuant to Board action
taken on January 2, 2018. 
 1,424,533 share increase (inclusive of December 18, 2017 and January 2, 2018 board approved
increases) ratified by stockholder consent on January 2, 2018. 
 Increased by 80,000 shares, from 1,942,643 to 2,022,643 shares,
pursuant to Board action taken on October 9, 2018 and later stockholder ratification. 
 Increased by 933,500 shares, from 2,022,643 to
2,956,143 shares, pursuant to Board action taken on March 4, 2019 (subject to delivery of requisite stockholder approval). 

  
 2. 

 (b) Substitute Awards. In connection with a merger or consolidation of an entity with
the Company or the acquisition by the Company of property or stock of an entity, the Board may grant Awards in substitution for any options or other stock or stock-based awards granted by such entity or an affiliate thereof. Substitute Awards may be
granted on such terms as the Board deems appropriate in the circumstances, notwithstanding any limitations on Awards contained in the Plan. Substitute Awards shall not count against the overall share limit set forth in Section 4(a), except as
may be required by reason of Section 422 and related provisions of the Code. 
 5. Stock Options 

(a) General. The Board may grant options to purchase Common Stock (each, an “Option”) and determine the number of shares of
Common Stock to be covered by each Option, the exercise price of each Option and the conditions and limitations applicable to the exercise of each Option, including conditions relating to applicable federal or state securities laws, as it considers
necessary or advisable. An Option that is not intended to be an Incentive Stock Option (as hereinafter defined) shall be designated a “Nonstatutory Stock Option”. 

(b) Incentive Stock Options. An Option that the Board intends to be an “incentive stock option” as defined in
Section 422 of the Code (an “Incentive Stock Option”) shall only be granted to employees of the Company, any of the Company’s present or future parent or subsidiary corporations as defined in Sections 424(e) or (f) of the
Code, and any other entities the employees of which are eligible to receive Incentive Stock Options under the Code. The Option shall be subject to and shall be construed consistently with the requirements of Section 422 of the Code, and without
limiting generality of the foregoing, the Option shall be deemed to include terms that comply with the eligibility standards described section 422(b) of the Code. Subject to the remaining provisions of this Section 5(b), if an Option intended
to qualify as an Incentive Stock Option does not so qualify, the Board may, at its discretion, amend the Plan and Award with respect to such Option so that such Option qualifies as an Incentive Stock Option. To the extent that the aggregate Fair
Market Value (determined at the time of grant) of Common Stock with respect to which Incentive Stock Options are exercisable for the first time by any Participant during any calendar year (under all plans of the Company and any affiliates) exceeds
$100,000 (or such other limit established in the Code) or otherwise does not comply with the rules governing Incentive Stock Options, the Options or portions thereof that exceed such limit (according to the order in which they were granted) or
otherwise do not comply with the rules will be treated as Nonstatutory Stock Options, notwithstanding any contrary provision of the applicable Award. The Company shall have no liability to a Participant, or any other party, if an Option (or any part
thereof) that is intended to be an Incentive Stock Option is not an Incentive Stock Option or for any action taken by the Board, including without limitation the conversion of an Incentive Stock Option to a Nonstatutory Stock Option. 

(c) Exercise Price. The Board shall establish the exercise price of each Option and specify the exercise price in the applicable option
agreement. 
 (d) Duration of Options. Each Option shall be exercisable at such times and subject to such terms and conditions as the
Board may specify in the applicable option agreement. 

  
 3. 

 (e) Exercise of Option. Options may be exercised by delivery to the Company of a
written notice of exercise signed by the proper person or by any other form of notice (including electronic notice) approved by the Board together with payment in full as specified in Section 5(f) for the number of shares for which the Option
is exercised. Shares of Common Stock subject to the Option will be delivered by the Company as soon as practicable following exercise. 

(f) Payment Upon Exercise. Common Stock purchased upon the exercise of an Option granted under the Plan shall be paid for as follows:

 (1) in cash or by check, payable to the order of the Company; 

(2) when the Common Stock is registered under the Exchange Act, except as may otherwise be provided in the applicable option agreement, by
(i) delivery of an irrevocable and unconditional undertaking by a creditworthy broker to deliver promptly to the Company sufficient funds to pay the exercise price and any required tax withholding or (ii) delivery by the Participant to the
Company of a copy of irrevocable and unconditional instructions to a creditworthy broker to deliver promptly to the Company cash or a check sufficient to pay the exercise price and any required tax withholding; 

(3) when the Common Stock is registered under the Exchange Act and to the extent provided for in the applicable option agreement or approved
by the Board, in its sole discretion, by delivery (either by actual delivery or attestation) of shares of Common Stock owned by the Participant valued at their fair market value as determined by (or in a manner approved by) the Board (“Fair
Market Value”), provided (i) such method of payment is then permitted under applicable law, (ii) such Common Stock, if acquired directly from the Company, was owned by the Participant for such minimum period of time, if any, as may be
established by the Board in its discretion and (iii) such Common Stock is not subject to any repurchase, forfeiture, unfulfilled vesting or other similar requirements; 

(4) to the extent permitted by applicable law and provided for in the applicable option agreement or approved by the Board, in its sole
discretion, by (i) delivery of a promissory note of the Participant to the Company on terms determined by the Board, or (ii) payment of such other lawful consideration as the Board may determine; or 

(5) by any combination of the above permitted forms of payment. 

6. Restricted Stock; Restricted Stock Units 

(a) General. The Board may grant Awards entitling recipients to acquire shares of Common Stock (“Restricted Stock”), subject
to the right of the Company to repurchase all or part of such shares at their issue price or other stated or formula price (or to require forfeiture of such shares if issued at no cost) from the recipient in the event that conditions specified by
the Board in the applicable Award are not satisfied prior to the end of the applicable restriction period or periods established by the Board for such Award. Instead of granting Awards for Restricted Stock, the Board may grant Awards entitling the
recipient to receive shares of Common Stock or cash to be delivered at the time such Award vests (“Restricted Stock Units”) (Restricted Stock and Restricted Stock Units are each referred to herein as a “Restricted Stock Award”).

  
 4. 

 (b) Terms and Conditions for All Restricted Stock Awards. The Board shall determine
the terms and conditions of a Restricted Stock Award, including the conditions for vesting and repurchase (or forfeiture) and the issue price, if any. 

(c) Additional Provisions Relating to Restricted Stock. 

(1) Dividends. Participants holding shares of Restricted Stock will be entitled to all ordinary cash dividends paid with respect to
such shares, unless otherwise provided by the Board. Unless otherwise provided by the Board, if any dividends or distributions are paid in shares, or consist of a dividend or distribution to holders of Common Stock other than an ordinary cash
dividend, the shares, cash or other property will be subject to the same restrictions on transferability and forfeitability as the shares of Restricted Stock with respect to which they were paid. Each dividend payment will be made no later than the
end of the calendar year in which the dividends are paid to shareholders of that class of stock or, if later, the 15th day of the third month following the date the dividends are paid to shareholders of that class of stock. 

(2) Stock Certificates. The Company may require that any stock certificates issued in respect of shares of Restricted Stock shall be
deposited in escrow by the Participant, together with a stock power endorsed in blank, with the Company (or its designee). At the expiration of the applicable restriction periods, the Company (or such designee) shall deliver the certificates no
longer subject to such restrictions to the Participant or if the Participant has died, to the beneficiary designated, in a manner determined by the Board, by a Participant to receive amounts due or exercise rights of the Participant in the event of
the Participant’s death (the “Designated Beneficiary”). In the absence of an effective designation by a Participant, “Designated Beneficiary” shall mean the Participant’s estate. 

7. Other Stock-Based Awards 
 Other
Awards of shares of Common Stock, and other Awards that are valued in whole or in part by reference to, or are otherwise based on, shares of Common Stock or other property, may be granted hereunder to Participants (“Other Stock-Based
Awards”), including without limitation stock appreciation rights (“SARs”) and Awards entitling recipients to receive shares of Common Stock to be delivered in the future. Such Other Stock-Based Awards shall also be available as a form
of payment in the settlement of other Awards granted under the Plan or as payment in lieu of compensation to which a Participant is otherwise entitled. Other Stock-Based Awards may be paid in shares of Common Stock or cash, as the Board shall
determine. Subject to the provisions of the Plan, the Board shall determine the terms and conditions of each Other Stock-Based Award, including any purchase price applicable thereto. 

8. Adjustments for Changes in Common Stock and Certain Other Events 

(a) Changes in Capitalization. In the event of any stock split, reverse stock split, stock dividend, recapitalization, combination of
shares, reclassification of shares, spin-off or other similar change in capitalization or event, or any dividend or distribution to holders of Common Stock other than an ordinary cash dividend, (i) the
number and class of securities 

  
 5. 

 
available under this Plan, (ii) the number and class of securities and exercise price per share of each outstanding Option, (iii) the number of shares subject to and the repurchase
price per share subject to each outstanding Restricted Stock Award, and (iv) the terms of each other outstanding Award shall be equitably adjusted by the Company (or substituted Awards may be made, if applicable) in the manner determined by the
Board; provided that, unless otherwise determined by the Board, such changes to the Options shall comply with section 1.424-1 of the Treasury Regulations. Without limiting the generality of the foregoing, in
the event the Company effects a split of the Common Stock by means of a stock dividend and the exercise price of and the number of shares subject to an outstanding Option are adjusted as of the date of the distribution of the dividend (rather than
as of the record date for such dividend), then an optionee who exercises an Option between the record date and the distribution date for such stock dividend shall be entitled to receive, on the distribution date, the stock dividend with respect to
the shares of Common Stock acquired upon such Option exercise, notwithstanding the fact that such shares were not outstanding as of the close of business on the record date for such stock dividend. 

(b) Reorganization Events. 

(1) Definition. A “Reorganization Event” shall mean: (a) any merger or consolidation of the Company with or into another
entity as a result of which all of the Common Stock of the Company is converted into or exchanged for the right to receive cash, securities or other property or is cancelled, (b) any exchange of all of the Common Stock of the Company for cash,
securities or other property pursuant to a share exchange transaction or (c) any liquidation or dissolution of the Company. 
 (2)
Consequences of a Reorganization Event on Awards Other than Restricted Stock Awards. In connection with a Reorganization Event, the Board may take any one or more of the following actions as to all or any (or any portion of) outstanding
Awards other than Restricted Stock Awards on such terms as the Board determines: (i) provide that Awards shall be assumed, or substantially equivalent Awards shall be substituted, by the acquiring or succeeding corporation (or an affiliate
thereof); provided that, unless otherwise determined by the Board, such assumption or substitution of the Options shall comply with section 1.424-1 of the Treasury Regulations, (ii) upon written notice to
a Participant, provide that the Participant’s unexercised Awards will terminate immediately prior to the consummation of such Reorganization Event unless exercised by the Participant within a specified period following the date of such notice,
(iii) provide that outstanding Awards shall become exercisable, realizable, or deliverable, or restrictions applicable to an Award shall lapse, in whole or in part prior to or upon such Reorganization Event, (iv) in the event of a
Reorganization Event under the terms of which holders of Common Stock will receive upon consummation thereof a cash payment for each share surrendered in the Reorganization Event (the “Acquisition Price”), make or provide for a cash
payment to a Participant equal to the excess, if any, of (A) the Acquisition Price times the number of shares of Common Stock subject to the Participant’s Awards (to the extent the exercise price does not exceed the Acquisition Price) over
(B) the aggregate exercise price of all such outstanding Awards and any applicable tax withholdings, in exchange for the termination of such Awards, (v) provide that, in connection with a liquidation or dissolution of the Company, Awards
shall convert into the right to receive liquidation proceeds (if applicable, net of the exercise price thereof and any applicable tax withholdings) and (vi) any combination of the foregoing. In taking any of the actions permitted under this
Section 8(b), the Board shall not be obligated by the Plan to treat all Awards, all Awards held by a Participant, or all Awards of the same type, identically. 

  
 6. 

 For purposes of clause (i) above, an Option shall be considered assumed if, following
consummation of the Reorganization Event, the Option confers the right to purchase, for each share of Common Stock subject to the Option immediately prior to the consummation of the Reorganization Event, the consideration (whether cash, securities
or other property) received as a result of the Reorganization Event by holders of Common Stock for each share of Common Stock held immediately prior to the consummation of the Reorganization Event (and if holders were offered a choice of
consideration, the type of consideration chosen by the holders of a majority of the outstanding shares of Common Stock); provided, however, that if the consideration received as a result of the Reorganization Event is not solely common stock of the
acquiring or succeeding corporation (or an affiliate thereof), the Company may, with the consent of the acquiring or succeeding corporation, provide for the consideration to be received upon the exercise of Options to consist solely of common stock
of the acquiring or succeeding corporation (or an affiliate thereof) equivalent in value (as determined by the Board) to the per share consideration received by holders of outstanding shares of Common Stock as a result of the Reorganization Event.

 (3) Consequences of a Reorganization Event on Restricted Stock Awards. Upon the occurrence of a Reorganization Event other than a
liquidation or dissolution of the Company, the repurchase and other rights of the Company under each outstanding Restricted Stock Award shall inure to the benefit of the Company’s successor and shall, unless the Board determines otherwise,
apply to the cash, securities or other property which the Common Stock was converted into or exchanged for pursuant to such Reorganization Event in the same manner and to the same extent as they applied to the Common Stock subject to such Restricted
Stock Award. Upon the occurrence of a Reorganization Event involving the liquidation or dissolution of the Company, except to the extent specifically provided to the contrary in the instrument evidencing any Restricted Stock Award or any other
agreement between a Participant and the Company, all restrictions and conditions on all Restricted Stock Awards then outstanding shall automatically be deemed terminated or satisfied. 

9. General Provisions Applicable to Awards 

(a) Transferability of Awards. Except as the Board may otherwise determine or provide in an Award, Awards shall not be sold, assigned,
transferred, pledged or otherwise encumbered by the person to whom they are granted, either voluntarily or by operation of law, except by will or the laws of descent and distribution or, other than in the case of an Incentive Stock Option, pursuant
to a qualified domestic relations order, and, during the life of the Participant, shall be exercisable only by the Participant. References to a Participant, to the extent relevant in the context, shall include references to authorized transferees.

 (b) Documentation. Each Award shall be evidenced in such form (written, electronic or otherwise) as the Board shall determine.
Each Award may contain terms and conditions in addition to those set forth in the Plan. 

  
 7. 

 (c) Board Discretion. Except as otherwise provided by the Plan, each Award may be
made alone or in addition or in relation to any other Award. The terms of each Award need not be identical, and the Board need not treat Participants uniformly. 

(d) Termination of Status. The Board shall determine the effect on an Award of the disability, death, termination or other cessation of
employment, authorized leave of absence or other change in the employment or other status of a Participant and the extent to which, and the period during which, the Participant, or the Participant’s legal representative, conservator, guardian
or Designated Beneficiary, may exercise rights under the Award. 
 (e) Withholding. The Company shall not be obligated to deliver
certificates, release from forfeiture, otherwise recognize a Participant’s unrestricted ownership in an Award or the cash or property proceeds therefrom, until the Company satisfies all applicable federal, state, and local or other income and
employment tax withholding obligations. In its sole discretion, the Company may satisfy such withholding obligations by any of the following means or by a combination of such means: (i) causing the Participant to tender to the Company cash
payment; (ii) withholding cash from an Award settled in cash; (iii) withholding from amounts otherwise payable by the Company to the Participant, including but not limited to additional withholding on the Participant’s salary or
wages, or from proceeds from the sale of Common Stock issued pursuant to an Award; (iv) delivery of shares of Common Stock, including shares retained from the Award creating the tax obligation, valued at their Fair Market Value; provided,
however, except as otherwise provided by the Board, that the total tax withholding where stock is being used to satisfy such tax obligations cannot exceed the Company’s minimum statutory withholding obligations (based on minimum statutory
withholding rates for federal and state tax purposes, including payroll taxes, that are applicable to such supplemental taxable income), and provided, further, shares surrendered to satisfy tax withholding requirements cannot be subject to any
repurchase, forfeiture, unfulfilled vesting or other similar requirements; or (v) by such other method as determined by the Board. 

(f) Amendment of Award. 

(1) The Board may amend, modify or terminate any outstanding Award, including but not limited to, substituting therefor another Award of the
same or a different type, changing the date of exercise or realization, and converting an Incentive Stock Option to a Nonstatutory Stock Option. The Participant’s consent to such action shall be required unless (i) the Board determines
that the action, taking into account any related action, would not materially and adversely affect the Participant’s rights under the Plan, (ii) the change is permitted under Section 8 hereof, or (iii) the change is to ensure
that an Option intended to qualify as an Incentive Stock Option qualifies as such. 
 (2) The Board may, without stockholder approval, amend
any outstanding Award granted under the Plan to provide an exercise price per share that is lower than the then- current exercise price per share of such outstanding Award. The Board may also, without stockholder approval, cancel any outstanding
award (whether or not granted under the Plan) and grant in substitution therefor new Awards under the Plan covering the same or a different number of shares of Common Stock and having an exercise price per share lower than the then- current exercise
price per share of the cancelled award. 

  
 8. 

 (g) Conditions on Delivery of Stock. The Company will not be obligated to deliver any
shares of Common Stock pursuant to the Plan or to remove restrictions from shares previously delivered under the Plan until (i) all conditions of the Award have been met or removed to the satisfaction of the Company, (ii) in the opinion of
the Company’s counsel, all other legal matters in connection with the issuance and delivery of such shares have been satisfied, including any applicable securities laws and any applicable stock exchange or stock market rules and regulations,
and (iii) the Participant has executed and delivered to the Company such representations or agreements as the Company may consider appropriate to satisfy the requirements of any applicable laws, rules or regulations. 

(h) Acceleration. The Board may at any time provide that any Award shall become immediately exercisable in full or in part, free of
some or all restrictions or conditions, or otherwise realizable in full or in part, as the case may be. 
 10. Miscellaneous 

(a) No Right To Employment or Other Status. No person shall have any claim or right to be granted an Award, and the grant of an Award
shall not be construed as giving a Participant the right to continued employment or any other relationship with the Company. The Company expressly reserves the right at any time to dismiss or otherwise terminate its relationship with a Participant
free from any liability or claim under the Plan, except as expressly provided in the applicable Award. 
 (b) No Rights As
Stockholder. Subject to the provisions of the applicable Award, no Participant or Designated Beneficiary shall have any rights as a stockholder with respect to any shares of Common Stock to be distributed with respect to an Award until becoming
the record holder of such shares. 
 (c) Effective Date and Term of Plan. The Plan shall become effective on the date on which it is
adopted by the Board. No Awards shall be granted under the Plan after the expiration of 10 years from the earlier of (i) the date on which the Plan was adopted by the Board or (ii) the date the Plan was approved by the Company’s
stockholders, but Awards previously granted may extend beyond that date. 
 (d) Amendment of Plan. The Board may amend, suspend or
terminate the Plan or any portion thereof at any time; provided that if at any time the approval of the Company’s stockholders is required as to any modification or amendment under Section 422 of the Code or any successor provision with
respect to Incentive Stock Options, the Board may not effect such modification or amendment without such approval. Unless otherwise specified in the amendment, any amendment to the Plan adopted in accordance with this Section 10(d) shall apply
to, and be binding on the holders of, all Awards outstanding under the Plan at the time the amendment is adopted, provided the Board determines that such amendment does not materially and adversely affect the rights of Participants under the Plan.

  
 9. 

 (e) Authorization of Sub-Plans. The Board may
from time to time establish one or more sub-plans under the Plan for purposes of satisfying applicable blue sky, securities or tax laws of various jurisdictions. The Board shall establish such sub-plans by adopting supplements to this Plan containing (i) such limitations on the Board’s discretion under the Plan as the Board deems necessary or desirable or (ii) such additional terms and
conditions not otherwise inconsistent with the Plan as the Board shall deem necessary or desirable. All supplements adopted by the Board shall be deemed to be part of the Plan, but each supplement shall apply only to Participants within the affected
jurisdiction and the Company shall not be required to provide copies of any supplement to Participants in any jurisdiction which is not the subject of such supplement. 

(f) Compliance with Code Section 409A. Unless otherwise expressly provided for in an Award, the Plan and Award will
be interpreted to the greatest extent possible in a manner that makes the Plan and the Awards granted hereunder exempt from Section 409A of the Code, and, to the extent not so exempt, in compliance with Section 409A of the Code. If the
Board determines that any Award granted hereunder is not exempt from and is therefore subject to Section 409A of the Code, the Award will incorporate the terms and conditions necessary to avoid the consequences specified in
Section 409A(a)(1) of the Code, and to the extent an Award is silent on terms necessary for compliance, such terms as deemed necessary by the Board in its sole discretion are hereby incorporated by reference into the Award. Without limiting the
generality of the foregoing, if shares of Common Stock are publicly traded, and if a Participant holding an Award that constitutes “deferred compensation” under Section 409A of the Code is a “specified employee” for purposes
of Section 409A of the Code, no distribution or payment of any amount that is due because of a “separation from service” (as defined in Section 409A of the Code without regard to alternative definitions thereunder) will be issued
or paid before the date that is six (6) months following the date of such Participant’s “separation from service” or, if earlier, the date of the Participant’s death, unless such distribution or payment can be made in a
manner that complies with Section 409A of the Code, and any amounts so deferred will be paid in a lump sum on the day after such six (6) month period elapses, with the balance paid thereafter on the original schedule. The Company shall
have no liability to a Participant, or any other party, if an Award that is intended to be exempt from, or compliant with, Section 409A of the Code is not so exempt or compliant or for any other action taken by the Board. 

(g) Governing Law. The provisions of the Plan and all Awards made hereunder shall be governed by and interpreted in accordance with the
laws of the State of Delaware, excluding choice-of-law principles of the law of such state that would require the application of the laws of a jurisdiction other than
such state. 

  
 10. 

 KEROS THERAPEUTICS, INC. 

2017 STOCK INCENTIVE PLAN 

CALIFORNIA SUPPLEMENT 
 Pursuant
to Section 10(e) of the Plan, the Board has adopted this supplement for purposes of satisfying the requirements of Section 25102(o) of the California Law: 

Any Awards granted under the Plan to a Participant who is a resident of the State of California on the date of grant (a “California
Participant”) shall be subject to the following additional limitations, terms and conditions: 
 1. Additional Limitations on Options. 

(a) Minimum Vesting Rate. Except in the case of Options granted to California Participants who are officers, directors, managers,
consultants or advisors of the Company or its affiliates (which Options may become exercisable at whatever rate is determined by the Board), Options granted to California Participants shall become exercisable at a rate of not less than 20% per year
over five years from the date of grant; provided, that, such Options may be subject to such reasonable forfeiture conditions as the Board may choose to impose and which are not inconsistent with Section 260.140.41 of the
California Regulations. 
 (b) Minimum Exercise Price. The exercise price of Options granted to California Participants may not be
less than 85% of the Fair Market Value of the Common Stock on the date of grant in the case of a Nonstatutory Stock Option or less than 100% of the Fair Market Value of the Common Stock on the date of grant in the case of an Incentive Stock Option;
provided, however, that if the California Participant is a person who owns stock possessing more than 10% of the total combined voting power of all classes of stock of the Company or its parent or subsidiary corporations, the exercise
price shall be not less than 110% of the Fair Market Value of the Common Stock on the date of grant. 
 (c) Maximum Duration of
Options. No Options granted to California Participants shall have a term in excess of 10 years measured from the Option grant date. 

(d) Minimum Exercise Period Following Termination. Unless a California Participant’s employment is terminated for cause (as
defined by applicable law, the terms of any contract of employment between the Company and such Participant, or in the instrument evidencing the grant of such Participant’s Option), in the event of termination of employment of such Participant,
such Participant shall have the right to exercise an Option, to the extent that he or she was otherwise entitled to exercise such Option on the date employment terminated, as follows: (i) at least six months from the date of termination, if
termination was caused by such Participant’s death or “permanent and total disability” (within the meaning of Section 22(e)(3) of the Code) and (ii) at least 30 days from the date of termination, if termination was caused
other than by such Participant’s death or “permanent and total disability” (within the meaning of Section 22(e)(3) of the Code). 

  
 A - 1 

 (e) Limitation on Repurchase Rights. If an Option granted to a California Participant
gives the Company the right to repurchase shares of Common Stock issued pursuant to the Plan upon termination of employment of such Participant, the terms of such repurchase right must comply with Section 260.140.41(k) of the California
Regulations. 
 2. Additional Limitations for Restricted Stock Awards. 

(a) Minimum Purchase Price. The purchase price for a Restricted Stock Award granted to a California Participant shall be not less than
85% of the Fair Market Value of the Common Stock at the time such Participant is granted the right to purchase shares under the Plan or at the time the purchase is consummated; provided, however, that if such Participant is a person who owns stock
possessing more than 10% of the total combined voting power or value of all classes of stock of the Company or its parent or subsidiary corporations, the purchase price shall be not less than 100% of the Fair Market Value of the Common Stock at the
time such Participant is granted the right to purchase shares under the Plan or at the time the purchase is consummated. 
 (b)
Limitation of Repurchase Rights. If a Restricted Stock Award granted to a California Participant gives the Company the right to repurchase shares of Common Stock issued pursuant to the Plan upon termination of employment of such Participant,
the terms of such repurchase right must comply with Section 260.140.42(h) of the California Regulations. 
 3. Additional Limitations for Other
Stock-Based Awards. The terms of all Awards granted to a California Participant under Section 7 of the Plan shall comply, to the extent applicable, with Section 260.140.41 or Section 260.140.42 of the California Regulations. 

4. Additional Requirement to Provide Information to California Participants. The Company shall provide to each California Participant and to each
California Participant who acquires Common Stock pursuant to the Plan, not less frequently than annually, copies of annual financial statements (which need not be audited). The Company shall not be required to provide such statements to key
employees whose duties in connection with the Company assure their access to equivalent information. 
 5. Additional Limitations on Timing of
Awards. No Award granted to a California Participant shall become exercisable, vested or realizable, as applicable to such Award, unless the Plan has been approved by the holders of a majority of the Company’s outstanding voting securities
within 12 months before or after the date the Plan was adopted by the Board. 
 6. Additional Limitations Relating to Definition of Fair Market
Value. For purposes of Section 1(b) and 2(a) of this supplement, “Fair Market Value” shall be determined in a manner not inconsistent with Section 260.140.50 of the California Regulations. 

7. Additional Restriction Regarding Recapitalizations, Stock Splits, Etc. For purposes of Section 8 of the Plan, in the event of a stock split,
reverse stock split, stock dividend, recapitalization, combination, reclassification or other distribution of the Company’s securities, the number of securities allocated to each California Participant must be adjusted proportionately and
without the receipt by the Company of any consideration from any California Participant. 

  
 A - 2 

 SIXTH AMENDMENT TO THE

 KEROS THERAPEUTICS, INC. 

2017 STOCK INCENTIVE PLAN 

A. Keros Therapeutics, Inc., a Delaware corporation (the “Company”) established the Company’s 2017 Stock
Incentive Plan by an original instrument adopted by the Company on February 6, 2017 (the “Plan”); 
 B.
The Plan currently provides for 2,956,143 shares of Common Stock to be reserved for issuance under the Plan; and 
 C. The Company
now wishes to amend the Plan to increase the number of shares of Common Stock reserved under the plan to 4,956,143 shares. 
 Effective
immediately, the Plan is amended as follows: 
  

	1.	 Section 4(a) the Plan is hereby amended and restated in its entirety as follows: 

“Number of Shares. Subject to adjustment under Section 8, Awards may be made under the Plan for up to 4,956,143 shares of
common stock, $0.0001 par value per share, of the Company (the “Common Stock”). If any Award expires or is terminated, surrendered or canceled without having been fully exercised, is forfeited in whole or in part (including as the result
of shares of Common Stock subject to such Award being repurchased by the Company at the original issuance price pursuant to a contractual repurchase right), or results in any Common Stock not being issued, the unused Common Stock covered by such
Award shall again be available for the grant of Awards under the Plan. Further, shares of Common Stock tendered to the Company by a Participant to exercise an Award shall be added to the number of shares of Common Stock available for the grant of
Awards under the Plan. However, in the case of Incentive Stock Options (as hereinafter defined), the foregoing provisions shall be subject to any limitations under the Code. Shares issued under the Plan may consist in whole or in part of authorized
but unissued shares or treasury shares. At no time while there is any Option (as defined below) outstanding and held by a Participant who was a resident of the State of California on the date of grant of such Option, shall the total number of shares
of Common Stock issuable upon exercise of all outstanding options and the total number of shares provided for under any stock bonus or similar plan or agreement of the Company exceed the applicable percentage as calculated in accordance with the
conditions and exclusions of Section 260.140.45 of the California Code of Regulations (the “California Regulations”), based on the shares of the Company which are outstanding at the time the calculation is made.” 

 

	2.	 In all other respects, the Plan remains the same. 

[Signature Page Follows] 

 The Company has caused this Sixth Amendment to the Company’s 2017 Equity Incentive Plan
to be executed this 2nd day of March, 2020. 
  

			
	KEROS THERAPEUTICS, INC.
		
	By:	 	/s/ Jasbir Seehra        
		 	Jasbir Seehra
		 	Chief Executive Officer

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