Exhibit 10.48

VICAL INCORPORATED

10390 Pacific Center Court

San Diego, CA 92121-4340

May 19, 2006

Jill M. Church

Vical Incorporated

10390 Pacific Center Court

San Diego, CA 92121-4340

 

Re: Amendment to Agreement Regarding Employment Terms

Dear Jill:

This Amendment (the “Amendment”) to your Letter Agreement with Vical
Incorporated (the “Company”) dated September 20, 2004 (the “Agreement”) amends
the terms and conditions of the Agreement to the extent provided herein. Except
as specifically amended by this Amendment, the terms and conditions of the
Agreement shall remain in full force and effect.

The attachment to the Agreement titled “Salary Continuation” is hereby deleted
in its entirety and replaced with the following:

“Salary Continuation”

Subject to mitigation, Vical will continue to pay your base compensation, at the
rate then in effect, for up to six months following the termination of your
employment if, prior to the expiration of your rights to salary continuation as
provided below:

 

  (i) Vical terminates your employment without your consent for any reason other
than Cause or Disability; or

 

  (ii) you voluntarily resign your employment for Good Reason

The salary continuation payments will cease in the event of your death. In order
to receive your salary continuation, you will be required to sign a release in a
form acceptable to Vical, of any and all claims that you may have against Vical.
The salary continuation rights described herein shall expire on the fourth
annual anniversary of the commencement of your employment; provided, however,
that such rights shall automatically renew for successive 1 year periods unless
the Company provides written notice to you at least 90 days prior to the next
scheduled expiration date that such rights will not be renewed.

Definitions:

 

  1.

Mitigation. The payments described in the section above titled “Salary
Continuation” shall be reduced on a dollar-for-dollar basis by any other
compensation earned by you for personal services performed as an employee or

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independent contractor during the six-month period following the termination of
your employment, including (without limitation) deferred compensation. You will
apply your best efforts to seek and obtain other employment or consulting
engagements, whether on a full- or part-time basis during such six-month period
in order to mitigate the Company’s obligations. At reasonable intervals, you
will report to Vical with respect to such efforts and any compensation earned
during such six-month period.

 

  2. Cause shall mean a failure to perform your duties, other than a failure
resulting from complete or partial incapacity due to physical or mental illness
or impairment, gross misconduct or fraud or conviction of, or a plea of “guilty”
or “no contest” to a felony.

 

  3. Disability shall mean that you, at the time your employment is terminated,
have performed substantially none of your duties under this Agreement for a
period of not less than three consecutive months as the result of your
incapacity due to physical or mental illness.

 

  4. Good Reason shall mean that you have incurred a material reduction in your
authority or responsibility or a reduction in base salary of more than 25%.”

This Amendment may be executed in two or more counterparts, each of which shall
be deemed an original and all of which together shall constitute one and the
same instrument. This Amendment shall be governed by and construed in accordance
with the laws of the State of California, without regard to conflicts of law
principles.

Please sign this Amendment and return it to the Company at your earliest
convenience.

 

Sincerely, VICAL INCORPORATED

By:

 

/s/ Vijay B. Samant

 

Vijay B. Samant

 

President and Chief Executive Officer

ACCEPTED AND AGREED:

/s/ Jill M. Church

Jill M. Church