ARE-SAN FRANCISCO NO. 17, LLC c/o Alexandria Real Estate Equities, Inc.

Exhibit 10.9(B)

ARE-SAN XXXXXXXXX XX. 00, XXX

x/x Xxxxxxxxxx Xxxx Xxxxxx Equities, Inc.

000 X. Xxxxxxxx Xxxxxxxxx, Xxxxx 000

Xxxxxxxx, Xxxxxxxxxx 00000

January 4, 2011

Achaogen, Inc.

0000 Xxxxxxxxx Xxxxx

Xxxxx Xxx Xxxxxxxxx, XX 00000

Attention: Finance Department

Re: 0000 Xxxxxxxxx Xxxxx, Xxxxx Xxx Xxxxxxxxx, Xxxxxxxxxx

Ladies and Gentlemen:

Achaogen, Inc. (“Tenant”) and ARE-San Francisco No. 17, LLC (“Landlord”) are parties to that certain Amended and Restated Lease Agreement dated December 29, 2010 (“Lease”) whereby Tenant leases certain premises at the above-referenced building. Initially capitalized terms used and not defined herein shall have the meanings set forth in the Lease.

Notwithstanding anything in the Lease to the contrary, Landlord and Tenant agree that (i) Base Rent for the month of March 2011 shall be $51,032.40 and (ii) Tenant’s Share of Operating Expenses for the month of March 2011 shall be 16.27%. Tenant shall continue to occupy and pay rent for Premises East (as defined in the Existing Lease) for the month of March 2011 under the MJ Research Sublease (as defined in the Existing Lease).

Except as specifically modified by this letter, all of the other terms and provisions of the Lease shall remain in full force and effect and unmodified by this letter. If there is a conflict between the terms of this letter and the terms of the Lease, then the terms of this letter shall govern and control in all respects.

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IN WITNESS WHEREOF, Landlord and Tenant have executed this Lease as of the day and year first above written.

TENANT:
ACHAOGEN, INC.,
a Delaware corporation
By:		/s/ Xxxx X. Xxxxx
Its:		CFO & VP, Operations
LANDLORD:
ARE-SAN FRANCISCO NO. 17, LLC, a Delaware limited liability company
By:		ALEXANDRIA REAL ESTATE EQUITIES, L.P.,
		a Delaware limited partnership, its managing member
		By:		ARE-QRS CORP.,
				a Maryland corporation, its general partner
				By:		/s/ Xxxx X. Xxxxxxx
				Its:		Vice President
						Real Estate Legal Affairs