Document:

EX-10.19

 Exhibit 10.19 

Parasol Therapeutics, Inc. 

c/o Polaris Venture Partners 
 1000
Winter Street, Suite 3350 
 Waltham, MA 02451 

September 26, 2008 
 Zachary Shriver, PhD 

Dear Zach: 
 It is with great pleasure that I
offer you regular full-time employment with Parasol Therapeutics, Inc. (“Parasol” or “the Company”). Your position will be Vice President, Research initially reporting directly to Parasol’s Chief Executive Officer. In
addition to performing duties and responsibilities associated with the position above, from time-to-time the Company may assign you other duties and responsibilities consistent with such position. Your effective date of employment will be on
Wednesday, October 1, 2008. We understand that during the period beginning on October 1, 2008 and ending on or about December 31, 2008 (the “Transition Period”) you will have some continuing obligations to your current
employer. 
 Commencing on January 1, 2009, you shall be paid on a semi-monthly basis at an annual base rate of $220,000 to be paid in
accordance with the Company’s standard payroll practices. You will also be eligible for a discretionary performance-based bonus with a target of 20% of your earned annual salary. During the Transition Period, you will receive a pro rata share
of your regular full-time salary. The specific details concerning your schedule, time commitment and compensation during the Transition Period will be determined by you and the Company during the course of the next two weeks. 

In addition, if your current employer fails to pay you a 2008 bonus, the Company will provide you with one or more cash payments to compensate
you for your loss of a 2008 bonus. You and the Company will mutually agree on the amount and timing of any such payments. 
 In
addition to eleven (11) Company-paid holidays and up to two (2) personal days, you will receive a total of fifteen (15) days of Earned Time Off per year of full-time employment, which is earned pro rata on a semi-monthly
basis. 
 As an incentive for you to share in the long-term growth of Parasol, it is our intention to recommend to the Parasol Board
of Directors (the “Board”) that you be granted a first incentive stock option to purchase 150,000 shares of Parasol’s common stock at an exercise price equal to the fair market value (as determined by the Board) on the date of the
grant. This first stock option shall vest over a four-year period, with 25% vesting twelve (12) months from your first day of employment with the Company, and an additional 2.083% vesting in equal monthly portions on the last day of the month
over the following thirty-six (36) months. In addition, we 

 
will recommend to the Board that you be granted a second incentive stock option to purchase 50,000 shares of Parasol’s common stock at an exercise price equal to the fair market value (as
determined by the Board) on the date of grant. This second stock option will vest based on the occurrence of the following milestone events: (a) 50% vesting upon the filing of the Company’s first IND and (b) 50% vesting at the time
the Company achieves a total of $10 million in cumulative funding from strategic partnering upfront cash payments and/or non-dilutive sources; provided that in each case the milestone event occurs by September 30, 2011 and you are an employee
of the Company at the time of the milestone event. 
 The Company is currently in the process of establishing its employee benefits package.
You will be eligible to participate in the employee benefit plans which the Company will offer to its full-time employees. Descriptions of the benefit plans will be made available upon request. Please note that once established, these plans may,
from time-to-time, be amended or terminated with or without prior notice. During the Transition Period and until such time as these plans have been established, the Company will reimburse you for any COBRA payments you may incur related to medical
and dental insurance premiums. 
 Your employment at all times will be at will, meaning that you are not being offered employment for a
definite period and that either you or the Company may terminate the employment relationship at any time for any reason. 
 As a condition
of your at-will employment, you will be required to sign the attached Invention and Non-Disclosure and Non-Competition and Non-Solicitation Agreements on or before your first day of employment. We acknowledge that during the Transition Period you
will have certain obligations to your current employer. We understand, however, that you are not subject to any agreements which restrict your activities for Parasol during the Transition Period and thereafter. By accepting this offer below, you
represent that you are not subject to any agreements which might restrict your conduct at the Company; and that you understand that if you become aware at any time during your employment with the Company that you are subject to any agreements which
might restrict your conduct at Parasol, you are required to immediately inform the Company of the existence of such agreements or your employment by the Company shall be subject to immediate termination. 

In addition, the Immigration Reform and Control Act requires employers to verify employment eligibility and identity of new employees. On your
first day of employment, you must provide us with appropriate documents to establish your eligibility to work in the United States (i.e. Social Security Card, Drivers’ License, U.S. Passport). We will not be able to employ you if you fail to
comply with this requirement. 
 Parasol maintains a smoke-free, drug-free workplace policy and supports equal employment opportunities for
all of its employees. 
 This letter, together with the Invention and Non-Disclosure and Non-Competition and Non-Solicitation Agreements,
will constitute the entire agreement as to your employment relationship with the Company and will supersede any prior agreements or understandings, whether in writing or oral. 

  
 - 2 - 

 Please indicate your acceptance of this offer and the terms and conditions thereof by signing and
returning to the Company this letter and the Invention and Non-Disclosure and Non-Competition and Non-Solicitation Agreements. 
 We are
looking forward to you joining the Parasol team. We are confident that you will find a great deal of challenge, satisfaction, and opportunity for personal and professional growth at the Company. 

 

	
	Sincerely,
	
	Parasol Therapeutics, Inc.
	
	Name: Kevin Bitterman

  

			
	Accepted by:
	
	 /s/ Kevin Bitterman

		
	Date:	 	 9/29/08

  
 - 3 - 

 December 7, 2012 

Zachary Shriver 
 21 Mount Pleasant Street 

Winchester, MA 01890 
  

	Re:	Terms of Employment Agreement 

 Dear Zach: 

I am pleased to provide you with additional terms and conditions of employment by Visterra, Inc. (the “Company” or
“Visterra”). The following sets forth the terms and conditions of our employment agreement with you. 
 In the event that
your employment were to be terminated by the Company without “Cause” or you resign your employment for “Good Reason” (as both terms are defined below), you will receive a severance benefit of six months of base salary
continuation which amount will be paid in accordance with the Company’s regular payroll practices beginning on the Payment Commencement Date (defined below). In addition, in the event of a Change of Control (as defined below), the number of
shares subject to your Options necessary to bring your total vesting of such Options to 350,000 shares will be automatically vested immediately prior to the closing of the Change of Control and the remaining 350,000 Shares subject to such Options
will vest in equal quarterly installments over the subsequent two years as long as your employment continues, or over the remaining vesting period of the option if shorter than 2 years. 

In the event of a Double Trigger Termination (as defined below), 100% of the remaining unvested portion of your Stock Option will
automatically become vested as of the date of your termination. The Company’s severance and vesting-acceleration obligations will be conditioned upon your execution and delivery to the Company of a reasonable release of claims within 60 days
following the date of termination, which provides for a release of any and all claims that you have or might have against the Company. The severance payments shall be paid or commence on the first payroll period following the date the waiver and
release becomes effective (the “Payment Commencement Date”). Notwithstanding the foregoing, if the 60th day following the date of termination occurs in the calendar year following the calendar year of the termination, then the Payment
Commencement Date shall be no earlier than January 1 of such subsequent calendar year. The term “Company” shall include the entity that survives the Change of Control. The severance benefits payable hereunder shall be subject to the
terms and conditions set forth in Exhibit 1. 
 “Cause” for termination shall mean: (i) commission of, or indictment
or conviction for, any felony or any crime involving moral turpitude; (ii) participation in any fraud against the Company; (iii) your substantial failure to perform (other than by reason of disability), or gross negligence in the

 performance of, your duties and responsibilities to the Company or any of its affiliates; (iv) other conduct
by you that is or could reasonably be anticipated to be harmful to the business, interests or reputation of the Company or any of its affiliates; or (v) your breach of any material provision of any agreement between you and the Company
including this agreement, as well as the Invention and Non-Disclosure Agreement, and the Non-Competition and Non-Solicitation Agreement signed by you on your first day of employment, as such may be amended from time to time. 

“Good Reason” shall mean any termination of your employment by you immediately following any of the following: (i) a
change in your principal work location despite your stated disagreement with such a change, to a location more than 60 miles from the Company’s current location in Cambridge, Massachusetts (travel for Company business shall not be deemed a
change in principal work location); (ii) a material reduction by the Company of your base salary; or (iii) a Reduction in Duties (as defined below); provided, however, that no such event or condition shall constitute Good
Reason unless (x) you give the Company a written notice of termination for Good Reason not more than 90 days after the initial existence of the condition, (y) the grounds for termination (if susceptible to correction) are not corrected by
the Company within 30 days of its receipt of such notice and (z) your termination of employment occurs within one year following the Company’s receipt of such notice. 

“Change of Control” means the closing of (i) a sale of all or substantially all of the assets of the Company, or
(ii) a stock tender or a merger, consolidation or similar event pursuant to a transaction or series of related transactions in which a third party acquires more than fifty percent (50%) of the equity voting securities of the Company
outstanding immediately prior to the consummation of such transaction or series of transactions, and the shareholders of the Company do not retain a majority of the equity voting securities of the surviving entity, other than (x) a merger,
conversion or other transaction the principal goal of which is to change the jurisdiction of incorporation of the Company, or (y) an equity security financing for the account of the Company in which capital stock of the Company is sold to one
or more institutional investors. 
 “Double Trigger Termination” means: either (i) a termination of your employment by
the Company without Cause within 12 months after a Change of Control; or (ii) termination of your employment by you for Good Reason within 12 months after a Change of Control. 

“Reduction in Duties” means: (i) prior to a Change of Control, a material reduction by the Company in your duties,
authority or responsibilities, including a demotion to a position less senior than Vice President; and (ii) after a Change of Control, a material reduction by the Company in your duties and responsibilities, provided that a change in title,
without a corresponding change in responsibility, shall not constitute a Reduction in Duties and, provided, further that, a change in scope of duties or responsibilities, solely as a result of the company becoming a subsidiary of another corporation
(including a publicly traded corporation), will not constitute a Reduction in Duties. Moreover, for clarity, if you receive a position after a Change in Control with the company that survives the Change of Control, and such position includes
responsibilities that are approximately commensurate with your responsibilities at Visterra prior to the Change of Control, then this also shall not be considered a Reduction in Duties, regardless of title. 

 If the terms of this offer are acceptable to you, please sign this letter in the place provided
and return it to me. Your signature on the copy of this letter and your delivery of the signed copy to the Company will evidence your agreement with the terms and conditions set forth herein. 

Thank you for your continued great contributions to Visterra’s success. 

 

	
	Sincerely,
	
	 /s/ Steven B. Brugger

	Steven B. Brugger, CEO

  

	
	Accepted and Agreed as of December 10, 2012
	
	 /s/ Zachary Shriver

	Zachary Shriver

 Exhibit 1 

Payments Subject to Section 409A 
 1.
Subject to this Exhibit 4, any severance payments that may be due under the offer letter shall begin only upon the date of your “separation from service” (determined as set forth below) which occurs on or after the termination of your
employment. The following rules shall apply with respect to distribution of the severance payments, if any, to be provided to you under the offer letter, as applicable: 

a. It is intended that each installment of the severance payments under the offer letter provided under shall be treated as a separate
“payment” for purposes of Section 409A. Neither the Company nor you shall have the right to accelerate or defer the delivery of any such payments except to the extent specifically permitted or required by Section 409A. 

b. If, as of the date of your “separation from service” from the Company, you are not a “specified employee” (within the
meaning of Section 409A), then each installment of the severance payments shall be made on the dates and terms set forth in the offer letter. 

c. If, as of the date of your “separation from service” from the Company, you are a “specified employee” (within the
meaning of Section 409A), then: 
 1. Each installment of the severance payments due under the offer letter that, in accordance with the
dates and terms set forth herein, will in all circumstances, regardless of when your separation from service occurs, be paid within the short-term deferral period (as defined under Section 409A) shall be treated as a short-term deferral within
the meaning of Treasury Regulation Section 1.409A-l(b)(4) to the maximum extent permissible under Section 409A and shall be paid on the dates and terms set forth in the offer letter; and 

2. Each installment of the severance payments due under the offer letter that is not described in this Exhibit 4,
Section 1(c)(i) and that would, absent this subsection, be paid within the six-month period following your “separation from service” from the Company shall not be paid until the date that is six months and one day after such
separation from service (or, if earlier, your death), with any such installments that are required to be delayed being accumulated during the six-month period and paid in a lump sum on the date that is six months and one day following your
separation from service and any subsequent installments, if any, being paid in accordance with the dates and terms set forth herein; provided, however, that the preceding provisions of this sentence shall not apply to any installment of payments if
and to the maximum extent that that such installment is deemed to be paid under a separation pay plan that does not provide for a deferral of compensation by reason of the application of Treasury Regulation 1.409A-1(b)(9)(iii) (relating to
separation pay upon an involuntary separation from service). Any installments that qualify for the exception under Treasury Regulation Section 1.409A-1(b)(9)(iii) must be paid no later than the last day of your second taxable year following the
taxable year in which the separation from service occurs. 

 2. The determination of whether and when your separation from service from the Company has occurred shall be made
and in a manner consistent with, and based on the presumptions set forth in, Treasury Regulation Section 1.409A11(h). Solely for purposes of this Exhibit A, Section 2, “Company” shall include all persons with whom the Company
would be considered a single employer under Section 414(b) and 414(c) of the Code. 
 3. The Company makes no representation or warranty and shall have
no liability to you or to any other person if any of the provisions of the Agreement (including this Exhibit) are determined to constitute deferred compensation subject to Section 409A but that do not satisfy an exemption from, or the
conditions of, that section. 
 4. All reimbursements and in-kind benefits provided under this offer letter shall be made or provided in accordance with the
requirements of Section 409A to the extent that such reimbursements or in-kind benefits are subject to Section 409A, including, where applicable, the requirements that (i) any reimbursement is for expenses incurred during your
lifetime (or during a shorter period of time specified in this offer letter), (ii) the amount of expenses eligible for reimbursement during a calendar year may not affect the expenses eligible for reimbursement in any other calendar year,
(iii) the reimbursement of an eligible expense will be made on or before the last day of the calendar year following the year in which the expense is incurred and (iv) the right to reimbursement is not subject to set off or liquidation or
exchange for any other benefit. 

 October 1, 2014 

Zachary Shriver, PhD 
 21 Mount Pleasant Street 

Winchester, MA 01890 
  

	Re:	Amendment to September 26, 2008 Offer Letter 

 Dear Zach: 

As we have discussed, in recognition of your service to the Company and to provide you with additional security in the event of certain employment
terminations, Visterra, Inc. (the “Company”) has agreed to amend and supplement the terms of your employment with the Company. This amendment (the “Amendment”) shall amend the terms of your September 26, 2008 offer letter
with the Company (the “Offer Letter”) and shall supersede and replace your December 7, 2012 offer letter amendment. Except as explicitly set forth below, the terms and conditions of your Offer Letter shall continue in full force and
effect. 
 Commencing as of the date on which you countersign this Amendment, you will be subject to the following additional terms and conditions of
employment: 
  

	 	5.	Equity Acceleration Upon a Change of Control. In the event you remain employed by the Company upon a “Change of Control” (as defined below), fifty percent (50%) of any unvested stock options you
may have as of such date will immediately vest and become exercisable in full. 

  

	 	a.	“Change of Control” means the closing of (i) a sale of all or substantially all of the assets of the Company, or (ii) a stock tender or a merger, consolidation or similar event pursuant to a
transaction or series of related transactions in which a third party acquires more than fifty percent (50%) of the equity voting securities of the Company outstanding immediately prior to the consummation of such transaction or series of
transactions, and the shareholders of the Company do not retain a majority of the equity voting securities of the surviving entity, other than (x) a merger, conversion or other transaction the principal goal of which is to change the
jurisdiction of incorporation of the Company, or (y) an equity security financing for the account of the Company in which capital stock of the Company is sold to one or more investors. 

 

	 	6.	Termination Without Cause or for Good Reason Prior to or More Than Twelve Months Following a Change of Control. In the event the Company terminates your employment without “Cause” (as defined below) or
you terminate your employment for “Good Reason” (as defined below) prior to or more than twelve (12) months following a Change of Control, and subject to your compliance with the conditions set forth in paragraph 4 below, you will be
eligible to receive the following severance benefits (the “Severance Benefits”): the Company will, for a period of twelve (12) months commencing on the “Payment Commencement Date” (as defined below), pay to you, as severance
pay, an amount equal to your base salary rate as of your termination date (the “Severance Pay”). 

	 	a.	“Cause” for termination shall mean: (i) commission of, or indictment or conviction for, any felony or any crime involving moral turpitude; (ii) participation in any fraud against the Company;
(iii) your substantial failure to perform (other than by reason of physical or mental illness or disability for a period of less than three consecutive months or in aggregate less than twenty-six weeks), or gross negligence in the performance
of, your duties and responsibilities to the Company or any of its affiliates; (iv) other conduct by you that is or could reasonably be anticipated to be harmful to the business, interests or reputation of the Company or any of its affiliates;
or (v) your breach of any material provision of any agreement between you and the Company, including any provision in the Invention and Non-Disclosure or Non-Competition and Non-Solicitation Agreements. 

 

	 	b.	“Good Reason” shall mean a termination of your employment by you for any of the following reasons: (i) without your written consent, a change in your principal work location to a location more than 60
miles from the Company’s current location in Cambridge, Massachusetts and to a location such that your daily commuting distance is increased (for the avoidance of doubt, travel for Company business shall not be deemed a change in principal work
location); (ii) without your written consent, a material reduction of your base salary; or (iii) without your written consent, a material reduction in your duties or responsibilities. To terminate your employment for Good Reason, you must
(i) provide written notice to the Company of the purported event giving rise to Good Reason within 90 days after it occurs, (ii) provide the Company with at least 30 days to cure, and (iii) if not cured, terminate your employment for
Good Reason within 30 days after the end of the cure period. 

  

	 	7.	Termination Without Cause or for Good Reason Within Twelve Months Following a Change of Control. In the event the Company terminates your employment without Cause or you terminate your employment for Good Reason
within twelve (12) months following a Change of Control, and subject to your compliance with the conditions set forth in paragraph 4 below, you will be eligible to receive the following change of control severance benefits (the “Change of
Control Severance Benefits”): (a) the Company will pay to you the Severance Pay at the time and in the manner set forth in paragraph 2 above, and (b) the entire unvested portion of any stock options you may have as of your termination
date will become vested and exercisable in full as of the Payment Commencement Date. 

  

	 	8.	 Severance Agreement. As a condition of your receipt of the Severance Benefits or the Change of Control Severance Benefits, as applicable, you
must execute and allow to become effective (within 60 days following your termination or such shorter period as the Company may specify) a severance and release of claims agreement in a form to be provided by the Company (which will include, at a
minimum, a release of all releasable claims against the Company and non-disparagement and cooperation obligations) (the “Severance Agreement”). Payment of the Severance Pay will begin on the first regular

	 	
payday after the Severance Agreement becomes effective (the “Payment Commencement Date”). Notwithstanding the foregoing, if the 60th
day following your date of termination occurs in the calendar year following the calendar year of your termination, then the Payment Commencement Date shall be no earlier than January 1 of such subsequent calendar year. The Severance Pay shall
be subject to the terms and conditions set forth in Exhibit A. 

  

	 	9.	Entire Agreement. This Amendment, along with the Offer Letter, constitutes the entire agreement between you and the Company regarding the terms and conditions of your employment, and this Amendment supersedes
your December 7, 2012 offer letter amendment, which is of no further force or effect. For the avoidance of doubt, your Invention and Non-Disclosure and Non-Competition and Non-Solicitation Agreements remain in full force and effect, and you
hereby reaffirm your obligations under such agreements. 

  

			
	Sincerely,
	
	 /s/ Brian J. G. Pereira

	By:	 	Brian J.G. Pereira, MD
	Chief Executive Officer

 The foregoing correctly sets forth the amended terms of my at-will employment with Visterra, Ins. 

 

	
	 /s/ Zachary Shriver

	Zachary Shriver, PhD

 Exhibit A 

Payments Subject to Section 409A 
 1.
Subject to this Exhibit A, any severance payments that may be due under the Amendment shall begin only upon the date of your “separation from service” (determined as set forth below) which occurs on or after the termination of your
employment. The following rules shall apply with respect to distribution of the severance payments, if any, to be provided to you under the offer letter, as applicable: 

(a) It is intended that each installment of the severance payments under the Amendment shall be treated as a separate “payment” for
purposes of Section 409A. Neither the Company nor you shall have the right to accelerate or defer the delivery of any such payments except to the extent specifically permitted or required by Section 409A. 

(b) If, as of the date of your “separation from service” from the Company, you are not a “specified employee” (within the
meaning of Section 409A), then each installment of the severance payments shall be made on the dates and terms set forth in the Amendment. 

(c) If, as of the date of your “separation from service” from the Company, you are a “specified employee” (within the
meaning of Section 409A), then: 
 (i) Each installment of the severance payments due under the Amendment that, in accordance with the
dates and terms set forth herein, will in all circumstances, regardless of when your separation from service occurs, be paid within the short-term deferral period (as defined under Section 409A) shall be treated as a short-term deferral within
the meaning of Treasury Regulation Section 1.409A-l(b)(4) to the maximum extent permissible under Section 409A and shall be paid on the dates and terms set forth in such Amendment; and 

(ii) Each installment of the severance payments due under the Amendment that is not described in this Exhibit A, Section 1(c)(i) and that
would, absent this subsection, be paid within the six-month period following your “separation from service” from the Company shall not be paid until the date that is six months and one day after such separation from service (or, if
earlier, your death), with any such installments that are required to be delayed being accumulated during the six-month period and paid in a lump sum on the date that is six months and one day following your separation from service and any
subsequent installments, if any, being paid in accordance with the dates and terms set forth herein; provided, however, that the preceding provisions of this sentence shall not apply to any installment of payments if and to the maximum extent that
that such installment is deemed to be paid under a separation pay plan that does not provide for a deferral of compensation by reason of the application of Treasury Regulation 1.409A-1 (b)(9)(iii) (relating to separation pay upon an involuntary
separation from service). Any installments that qualify for the exception under Treasury Regulation Section 1.409A-I(b)(iii) must be paid no later than the last day of your second taxable year following the taxable year in which the separation
from service occurs. 
 2. The determination of whether and when your separation from service from the Company has occurred shall be made and in a manner
consistent with, and based on the presumptions set forth in, Treasury Regulation Section 1.409A-I (h). Solely for purposes of this Exhibit A, Section 2, “Company” shall include all persons with whom the Company would be
considered a single employer under Section 414(b) and 414(c) of the Code. 
 3. The Company makes no representation or warranty and shall have no
liability to you or to any other person if any of the provisions of the Amendment (including this Exhibit) are determined to constitute deferred compensation subject to Section 409A but do not satisfy an exemption from, or the conditions of,
that section.EX-10.20

 Exhibit 10.20 

August 23, 2013 
 Gregory Leon Miller 

 

	Re:	Employment Offer Letter 

 Dear Greg: 

On behalf of Visterra, Inc. (the “Company” or “Visterra”), I am pleased to set forth in this letter (the “Employment
Offer Letter”) the terms and conditions of your employment with the Company, should you accept our offer. 
 1. Position.
You will be the Vice President of Business Development & Strategic Planning, reporting to the Company’s Chief Operating Officer (the “COO”). You will be expected to devote your full business time and your best professional
efforts to the performance of your duties and responsibilities for the Company and to abide by all Company policies and procedures, as in effect from time to time. You will be expected to perform the duties of your position and such other duties as
reasonably may be assigned to you from time to time by the COO. 
 2. Start Date/Nature of Relationship. 

(a) Your employment with the Company will begin on October 3, 2013 (the “Start Date”). 

(b) No provision of this letter shall be construed to create a promise of employment for any specific period of time. Your employment with the
Company is at-will employment, which may be terminated by you or the Company at any time, for any reason, with or without cause or notice. 

3. Compensation. 

(a) Base Salary. The Company will pay you a base salary at the rate of $20,000 per monthly pay period (which if annualized equals
$240,000 per year), payable in installments in accordance with the regular payroll practices of the Company, less all applicable taxes and withholdings. 

(b) Annual Bonus. Following the end of the 2014 calendar year and each calendar year thereafter, you will be eligible to receive an
annual cash bonus. The target amount of this bonus will be 25% of your then current annualized base salary. The actual amount of any annual bonus may be more or less than the above-stated target amount, and will be determined by the Board based on
the Company’s performance and your performance during the applicable calendar year, as determined by the Board in its sole discretion. Any annual bonus will be determined and paid within 45 days after the end of the applicable calendar year.
You must be employed by the Company on the date of payment in order to be eligible for and to earn a bonus award, as it also serves as an incentive to remain employed by the Company. Any bonus will be subject to all applicable taxes and
withholdings. 
 (c) Signing Bonus. You shall receive as a signing bonus a one-time, lump sum 

  
 1 

 
payment of $20,000, less all applicable taxes and withholdings, on the Company’s first regular payroll date following your Start Date. 

(d) Retention Bonus. Provided you remain employed by the Company on October 1, 2014, you will receive as a retention bonus a
one-time, lump sum payment of $20,000, less all applicable taxes and withholdings, on the Company’s first regular payroll date following October 1, 2014. 

(e) Equity. Following the Start Date, and subject to approval of the Board, the Company will grant you a stock option to purchase
421,521 shares of the Company’s common stock, $0.0001 par value per Share (“Common Stock”), at a price equal to the fair market value of the Common Stock on the date of grant, which price is expected to be $0.23 per share (the
“Base Option Grant”). The purchase and sale of the Shares shall be made pursuant to the Company’s 2008 Stock Incentive Plan and shall be governed by a Stock Option Agreement, which shall contain, among other things, vesting
requirements such that: 25% of the Shares shall vest and become exercisable on the first anniversary of the Start Date; and the remaining 75% shall vest and become exercisable quarterly over the subsequent three year period. The Base Option Grant
will be treated as an “Incentive Stock Option” to the extent permissible under the Internal Revenue Codes of 1986, as amended (the “Code”) and shall otherwise be treated as a nonstatutory stock option. You will be responsible for
payment of all taxes (and related withholding obligations) that you incur as a result of exercise of the option or receipt of contingent consideration. 

4. Equity Acceleration Upon a Change of Control. In the event you remain employed by the Company upon a “Change of
Control” (as defined in this section below), fifty percent (50%) of any unvested stock options you may have as of such date will immediately vest and become exercisable in full. 

(a) “Change of Control” means the closing of (i) a sale of all or substantially all of the assets of the Company, or
(ii) a stock tender or a merger, consolidation or similar event pursuant to a transaction or series of related transactions in which a third party acquires more than fifty percent (50%) of the equity voting securities of the Company
outstanding immediately prior to the consummation of such transaction or series of transactions, and the shareholders of the Company do not retain a majority of the equity voting securities of the surviving entity, other than (x) a merger,
conversion or other transaction the principal goal of which is to change the jurisdiction of incorporation of the Company, or (y) an equity security financing for the account of the Company in which capital stock of the Company is sold to one
or more institutional investors. 
 5. Termination Without Cause or for Good Reason Prior to or More Than Twelve Months
Following a Change of Control. In the event the Company terminates your employment without “Cause” or you terminate your employment for “Good Reason” (as both terms are defined in this section below) prior to or more than
twelve (12) months following a Change of Control, and subject to your compliance with the conditions set forth in section 7 below, you will be eligible to receive the following severance benefits (the “Severance Benefits”): the
Company will, for a period of twelve (12) months following your termination of employment, continue to pay to you, as severance pay, an amount equal to your base salary rate as of your termination date (the “Severance Pay”).

 (a) “Cause” for termination shall mean: (i) commission of, or indictment or conviction for, any felony or any crime
involving moral turpitude; (ii) participation in any fraud 

  
 2 

 (b) against the Company; (iii) your substantial failure to perform (other than by reason of
physical or mental illness or disability for a period of less than three consecutive months or in aggregate less than twenty-six weeks), or gross negligence in the performance of, your duties and responsibilities to the Company or any of its
affiliates; (iv) other conduct by you that is or could reasonably be anticipated to be harmful to the business, interests or reputation of the Company or any of its affiliates; or (v) your breach of any material provision of any agreement
between you and the Company, including any provision in this Employment Offer Letter or the Ancillary Agreements (as defined in Section 12 below). 

(c) “Good Reason” shall mean a termination of your employment by you for any of the following reasons: (i) without your written
consent, a change in your principal work location to a location more than 60 miles from the Company’s current location in Cambridge, Massachusetts and to a location such that your daily commuting distance is increased (for the avoidance of
doubt, travel for Company business shall not be deemed a change in principal work location); (ii) without your written consent, a material reduction of your base salary; or (iii) without your written consent, a material reduction in your
duties or responsibilities. To terminate your employment for Good Reason, you must (i) provide written notice to the Company of the purported event giving rise to Good Reason within 90 days after it occurs, (ii) provide the Company with at
least 30 days to cure, and (iii) if not cured, terminate your employment for Good Reason within 30 days after the end of the cure period. 

6. Termination Without Cause or for Good Reason Within Twelve Months Following a Change of Control. In the event the
Company terminates your employment without Cause or you terminate your employment for Good Reason within twelve (12) months following a Change of Control, and subject to your compliance with the conditions set forth in section 7 below:
(a) the Company will pay to you the Severance Pay, and (b) the entire unvested portion of any stock options you may have as of your termination date will become vested and exerciseable in full (collectively, the Change of Control Severance
Benefits”). 
 7. Severance Agreement. As a condition of your receipt of the Severance Benefits or the
Change of Control Severance Benefits, as applicable, you must execute and allow to become effective (within 60 days following your termination or such shorter period as the Company may specify) a severance and release of claims agreement provided by
the Company (the “Severance Agreement”), which among other things will provide for a release of any and all claims that you have or might have against the Company. Payment of the Severance Pay will begin on the first regular payday after
the Severance Agreement becomes effective (the “Payment Commencement Date”). Notwithstanding the foregoing, if the 60th day following your date of termination occurs in the calendar year
following the calendar year of your termination, then the Payment Commencement Date shall be no earlier than January 1 of such subsequent calendar year. The Severance Pay shall be subject to the terms and conditions set forth in Exhibit A.

 8. Benefits. You may participate in all employee benefit plans made generally available by the Company from time
to time to its employees, provided that you are eligible under (and subject to all provisions of) the plan documents that govern those plans. These benefits, of course, may be modified or changed from time to time at the sole discretion of the
Board, and the provision of such benefits to you in no way changes or impacts your status as an at-will employee. 
 9.
Vacation and Holidays. You will be eligible for a maximum of twenty (20) days of paid vacation per calendar year, to be taken at such times as may be approved in advance by the Company. The number of vacation days for which you
are eligible shall accrue at the rate of 1.67  

  
 3 

 
days per month that you are employed during such calendar year. You may not carry over more than five (5) days of vacation time from one calendar year to the next; any additional accrued but
unused vacation days will be forfeited at the end of the calendar year. In addition, you will be eligible to take those holidays observed by the Company. 

10. Business Expenses. The Company will pay or reimburse you for all reasonable business expenses incurred or paid by you
in the performance of your duties and responsibilities for the Company, subject to any maximum annual limit and other restrictions on such expenses set by the Company and to such reasonable substantiation and documentation as it may specify from
time to time. Any reimbursements shall be subject to the terms and conditions set forth in Exhibit A, Section 4. 
 11.
Before You Start. Your employment with the Company is conditioned on your eligibility to work in the United States. You agree to provide to the Company, within three (3) days of your date of hire, documentation proving your
eligibility to work in the United States, as required by the Immigration Reform and Control Act of 1986. To that end, a copy of an I-9 Form is enclosed for your information. Please bring the appropriate documents listed on that form with you when
you report to work. 
 12. Confidentiality and Other Continuing Obligations. The Company considers the
protection of its confidential information, proprietary materials and goodwill to be extremely important. You may not discuss the fact or terms of this Employment Offer Letter or any discussions concerning your employment with anyone other than the
CEO and members of your immediate family (and, if relevant, your financial advisor or lawyer). In addition, as a condition of your employment, you are required to carefully review and then sign the Invention and Non-Disclosure Agreement and the
Non-Competition and Non-Solicitation Agreement (collectively, the “Ancillary Agreements”) enclosed with this Employment Offer Letter. Your obligations under the Ancillary Agreements shall remain in full force and effect pursuant to
the terms thereof. 
 13. No Conflict. You hereby represent and warrant to the Company that your signing of this
Employment Offer Letter and the performance of your obligations hereunder will not breach or be in conflict with any other agreement to which you are a party or are bound, and that you are not now subject to any covenants against competition or
similar covenants or any court orders that prevent you from entering into employment with the Company or carrying out your responsibilities for the Company, or that are in any way inconsistent with the terms of this Employment Offer Letter. You
agree that you will not disclose to or use on behalf of the Company any proprietary or confidential information of a third party. You represent and agree that you will not be an employee of any other company as of the Start Date. 

14. Miscellaneous. This Employment Offer Letter and the Ancillary Agreements constitute our entire agreement regarding
the terms and conditions of your employment with the Company. They supersede any prior proposals, agreements, or other promises or statements (whether oral or written) regarding the terms of your employment. The terms of your employment shall be
governed by the laws of The Commonwealth of Massachusetts, without regard to its principles of conflicts of laws. 
 [Signature
page follows] 

  
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 If the terms of this Employment Offer Letter are acceptable to you, please sign this letter in the space provided
below and return it to me, along with signed copies of the Ancillary Agreements, no later than August 27, 2013. 
 We are excited for you to join our
team and are confident that you will make a major contribution to our unique and exciting enterprise. 
  

			
	Sincerely,
	
	VISTERRA, INC.
	
	/s/ Brian J.G. Pereira, MD
	By:	 	 Brian J.G. Pereira, MD
 Chief Executive
Officer

 The foregoing correctly sets forth the terms of my at-will employment with Visterra, Inc. I am not relying on any
representations other than those set forth above. 
  

	
	/s/ Gregory Leon Miller
	Gregory Leon Miller

  
 5 

 Exhibit A 

Payments Subject to Section 409A 

1. Subject to this Exhibit A, any severance payments that may be due under the Employment Offer Letter shall begin only upon the date of your
“separation from service” (determined as set forth below) which occurs on or after the termination of your employment. The following rules shall apply with respect to distribution of the severance payments, if any, to be provided to you
under the offer letter, as applicable: 
 (a) It is intended that each installment of the severance payments under the Employment Offer
Letter provided under shall be treated as a separate “payment” for purposes of Section 409A. Neither the Company nor you shall have the right to accelerate or defer the delivery of any such payments except to the extent specifically
permitted or required by Section 409A. 
 (b) If, as of the date of your “separation from service” from the Company, you are
not a “specified employee” (within the meaning of Section 409A), then each installment of the severance payments shall be made on the dates and terms set forth in the Employment Offer Letter. 

(c) If, as of the date of your “separation from service” from the Company, you are a “specified employee” (within the
meaning of Section 409A), then: 
 (i) Each installment of the severance payments due under the Employment Offer Letter that, in
accordance with the dates and terms set forth herein, will in all circumstances, regardless of when your separation from service occurs, be paid within the short-term deferral period (as defined under Section 409A) shall be treated as a
short-term deferral within the meaning of Treasury Regulation Section 1.409A-1(b)(4) to the maximum extent permissible under Section 409A and shall be paid on the dates and terms set forth in such offer letter; and 

(ii) Each installment of the severance payments due under the Employment Offer Letter that is not described in this Exhibit A, Section
l(c)(i) and that would, absent this subsection, be paid within the six-month period following your “separation from service” from the Company shall not be paid until the date that is six months and one day after such separation from
service (or, if earlier, your death), with any such installments that are required to be delayed being accumulated during the six-month period and paid in a lump sum on the date that is six months and one day following your separation from service
and any subsequent installments, if any, being paid in accordance with the dates and terms set forth herein; provided, however, that the preceding provisions of this sentence shall not apply to any installment of payments if and to the maximum
extent that that such installment is deemed to be paid under a separation pay plan that does not provide for a deferral of compensation by reason of the application of Treasury Regulation 1.409A-1 (b)(9)(iii) (relating to separation pay upon an
involuntary separation from service). Any installments that qualify for the exception under Treasury Regulation Section 1.409A-l(bX9)(iii) must be paid no later than the last day of your second taxable year following the taxable year in which
the separation from service occurs. 

  
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 2. The determination of whether and when your separation from service from the Company has
occurred shall be made and in a manner consistent with, and based on the presumptions set forth in, Treasury Regulation Section 1.409A-1 (h). Solely for purposes of this Exhibit A, Section 2, “Company” shall include all persons
with whom the Company would be considered a single employer under Section 414(b) and 414(c) of the Code. 
 3. The Company makes no
representation or warranty and shall have no liability to you or to any other person if any of the provisions of the Employment Offer Letter (including this Exhibit) are determined to constitute deferred compensation subject to Section 409A but
that do not satisfy an exemption from, or the conditions of, that section. 
 4. All reimbursements and in-kind benefits provided under the
Employment Offer Letter shall be made or provided in accordance with the requirements of Section 409A to the extent that such reimbursements or in-kind benefits are subject to Section 409A, including, where applicable, the requirements
that (i) any reimbursement is for expenses incurred during your lifetime (or during a shorter period of time specified in the Employment Offer Letter), (ii) the amount of expenses eligible for reimbursement during a calendar year may not
affect the expenses eligible for reimbursement in any other calendar year, (iii) the reimbursement of an eligible expense will be made on or before the last day of the calendar year following the year in which the expense is incurred and
(iv) the right to reimbursement is not subject to set off or liquidation or exchange for any other benefit. 

  
 7

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