Exhibit 10.16

Amendment No. 6 to Sublease

This Amendment No. 6 (the “Sixth Amendment”) is effective as of September 1,
2013 (the “Sixth Amendment Effective Date”) by and between Silver Creek
Pharmaceuticals (“Subtenant”) and FibroGen, Inc. (“FibroGen”). This Sixth
Amendment amends the Sublease entered into by and between Subtenant and FibroGen
on August 6, 2010 (the “Sublease”), as amended pursuant to the First Amendment
on February 1, 2011, the Second Amendment on May 1, 2011, the Third Amendment on
June 15, 2011, the Fourth Amendment on August 1, 2011 and the Fifth Amendment on
September 1, 2012 (the “Prior Amendments”). Subtenant and FibroGen shall be
referred to individually herein as a “Party”, and collectively as, the
“Parties”.

Whereas, Subtenant is presently subletting certain office and laboratory space;
and

Whereas, Subtenant wishes to continue to sublease certain designated office and
laboratory space from FibroGen in the 409 Building; and

Whereas, Effective December 15, 2013, Subtenant wishes to add 163 square feet to
the space that Subtenant is currently occupying in the Vivarium Area.

Now, Therefore, for good and valuable consideration, the receipt and sufficiency
of which is hereby acknowledged, the Parties agree as follows:

 

  •   Unless otherwise defined herein, all capitalized terms and phrases used in
this Sixth Amendment shall have the meaning ascribed to them in the Sublease as
amended by the Prior Amendments.

 

  •   Effective December 15, 2013, Section 2.1 of the Sublease is hereby deleted
in its entirety and replaced with the following:

“2.1 Conditioned upon receipt of Master Lessor’s written consent, FibroGen
hereby subleases to Subtenant and Subtenant hereby takes from FibroGen certain
real property as described below (the “Subleased Premises”) comprising of
approximately the total grossed-up footprint equaling one thousand eight hundred
and seventy-eight point thirty-three (1,878.33) square feet as follows:

 

  •   In Vivarium Area #2001, #2012, #2014, #2016, #2018 and #2024. Total
grossed-up area equals five hundred and eleven point thirty-three
(511.33) square feet.

 

  •    1⁄2 of Laboratory #4034/#4036. Total grossed-up area equals eight hundred
and thirty (830) square feet.

 

  •   Office Area #5202 and Open Area #5221. Total grossed-up area equals five
hundred and thirty seven (537) square feet.

 

  •   The Subleased Premises may be increased upon the mutual agreement of the
Parties hereto in the form of a signed amendment to this Sublease. However, it
is expressly understood that neither Party hereto is obligated to enter into
such an amendment.”

 

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  •   Section 3.2 of the Sublease is hereby deleted in its entirety and replaced
with the following:

“3.2 This Sublease will expire on:

 

  •   June 1, 2014 (“Expiration Date”)

 

  •   Subtenant shall have the option to extend term of lease for one additional
six (6) month term by giving thirty (30) days written notice no later than
thirty (30) days from the Expiration Date stated in Section 3.2a”

 

  •   Section 4.1 of the Sublease is hereby amended with the following:

“4.1 Subtenant shall pay a monthly rent (“Rent”) to FibroGen for the Subleased
Premises according to the following Schedule:

 

Months

   Rent/Sq.Ft./Mo.    Total Sq. Ft.      Amount/Mo.  

September 1, 2010-January 31, 2011
(Lab/Office)

   $6.80      761.00      $ 5,174.80   

February 1, 2011-April 30, 2011
(Lab/Office)

   $6.80      1271.00      $ 8,642.80   

May 1, 2011-June 14, 2011
(Lab/Office)

   $6.80      1354.00      $ 9,207.20   

June 15, 2011-July 31, 2011
(Lab/Office/Vivarium)

   $6.50/Vivarium      348.33       $ 2,264.15       $6.80/Office/Lab     
1354.00       $ 9,207.20            Total Sq. Ft.         Total Amt./Mo.      
     1738.33      $ 11,471.35   

August 1, 2011-August 7, 2011
(Lab/Office/Vivarium)

   $6.50/Vivarium      348.33       $ 511.28       $6.80/Office/Lab      1354.00
      $ 2,079.00            Total Sq. Ft.         Total Amt.            1715.33
     $ 2,590.28   

August 8, 2011-August 31, 2011*
(Lab/Office/Vivarium)

   $6.50/Vivarium      348.33       $ 1,752.87       $6.60/Office/Lab     
1367.00       $ 6,984.96            Total Sq. Ft.         Total Amt.           
1715.33      $ 8,737.83   

September 1, 2011-December 14, 2013
(Lab/Office/Vivarium)

   $6.50/Vivarium      348.33       $ 2,264.15       $6.60/Office/Lab     
1367.00       $ 9,022.20            Total Sq. Ft.         Total Amt./Mo.      
     1715.33      $ 11,286.35   

December 15, 2013-June 1, 2014
(Lab/Office/Vivarium)

   $6.50/Vivarium      511.33       $ 3,323.65       $6.60/Office/Lab     
1367.00       $ 9,022.20            Total Sq. Ft.         Total Amt./Mo.      
     1878.33      $ 12,345.85   

 

* Note: Pro-Rated Rent Payment”

 

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  •   This Sixth Amendment, together with the Sublease, as amended by the Prior
Amendments, contains the entire understanding of the Parties with respect to the
subject matter hereof. Except as otherwise provided herein and in the Prior
Amendments, the Sublease has not been modified or amended and remains in full
force and effect. All express or implied agreements and understandings that
conflict with the terms of this Sixth Amendment, either oral or written,
heretofore made with respect to subject matter herein are expressly superseded
by this Sixth Amendment.

 

  •   This Sixth Amendment may be executed in counterparts, each of which shall
be deemed an original, and all of which together shall constitute one and the
same instrument. Counterparts may be signed and delivered by facsimile and/or
via portable document format (pdf) (or similar format), each of which shall be
binding when sent.

In Witness Whereof, the Parties have executed this Sixth Amendment to the
Sublease as of the Sixth Amendment Effective Date.

 

FibroGen, Inc.     Silver Creek Pharmaceuticals By:   /s/ Pat Cotroneo     By:  
/s/ Matthew Onsum Name:   Pat Cotroneo     Name:   Matthew Onsum Title:   CFO  
  Title:   President Date:   12/12/13     Date:   12/9/13

 

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