JOINDER AGREEMENT

Exhibit 10.21

JOINDER AGREEMENT

This Joinder Agreement (the “Joinder Agreement”) is made and dated as of June 3, 2014, and is entered into by and between ZP Holdings, Inc., a Delaware corporation (“ZP Holdings”), and Hercules Technology Growth Capital, Inc., a Maryland corporation, as a Lender.

RECITALS

A. ZP Holdings’s Affiliate, Zosano Pharma, Inc. (“Company”) has entered into that certain Loan and Security Agreement dated June 3, 2014 with Lender, as such agreement may be amended (the “Loan Agreement”), together with the other agreements executed and delivered in connection therewith;

B. ZP Holdings acknowledges and agrees that it will benefit both directly and indirectly from Company’s execution of the Loan Agreement, the Warrant and the other agreements executed and delivered in connection therewith;

AGREEMENT

NOW THEREFORE, ZP Holdings and Lender agree as follows:

[REMAINDER OF PAGE INTENTIONALLY LEFT BLANK]

Joinder Agreement - ZP Holdings

[SIGNATURE PAGE TO JOINDER AGREEMENT]

Joinder Agreement - ZP Holdings

EXHIBIT C

NAME, LOCATIONS, AND OTHER INFORMATION FOR ZP HOLDINGS

1. ZP Holdings represents and warrants to Lender that ZP Holdings’ current name and organizational status as of the Closing Date is as follows:

2. ZP Holdings represents and warrants to Lender that for five (5) years prior to the Closing Date, ZP Holdings did not do business under any other name or organization or form except the following:

Name: none

Used during dates of: n/a

Type of Organization:

State of organization:

Organization file Number:

ZP Holdings’ fiscal year ends on December 31

ZP Holdings’ federal employer tax identification number is: 45 ###-###-####

3. ZP Holdings represents and warrants to Lender that its chief executive office is located at 34790 Ardentech Court, Fremont, CA 94555.

EXHIBIT D

ZP HOLDINGS PATENTS, REGISTERED TRADEMARKS, REGISTERED

COPYRIGHTS, APPLICATIONS FOR THE FOREGOING AND MATERIAL

LICENSES

None.

Schedule 1

Subsidiaries

Borrower (Zosano Pharma, Inc.), a Delaware corporation located at 34790 Ardentech Court, Fremont, CA 94555.

Zosano, Inc. (formerly named Eco Planet Corp.), a Delaware corporation located at 34790 Ardentech Court, Fremont, CA 94555.

ZP Holdings is the ultimate parent of ZP Group LLC, a Delaware limited liability company and wholly owned subsidiary of Borrower located at 34790 Ardentech Court, Fremont, CA 94555.

Schedule 1A

Existing Permitted Indebtedness

Secured Promissory Note in the original principal amount of $8,556,533 issued to BioMed Realty Holdings, Inc. by ZP Holdings, Inc. (and subsequently assigned by BioMed Realty Holdings, Inc. to its affiliate BMV Direct SOTRS LP), which Secured Promissory Note is subordinated to the Secured Obligations pursuant to the Subordination Agreement. As of the Closing Date, the principal and interest outstanding under such note totals $10,065,540.00.

Convertible Promissory Note dated September 9, 2013 in the original principal amount of $303,372 issued to BMV Direct SO LP by ZP Holdings, Inc. As of the Closing Date, the principal and interest outstanding under such note totals $321,125.50.

Convertible Promissory Note dated September 9, 2013 in the original principal amount of $991,047.43 issued to BMV Direct SOTRS LP by ZP Holdings, Inc. As of the Closing Date, the principal and interest outstanding under such note totals $1,049,044.07.

Convertible Promissory Note dated September 9, 2013 in the original principal amount of $1,159,532.21 issued to New Enterprise Associates 12, Limited Partnership by ZP Holdings, Inc. As of the Closing Date, the principal and interest outstanding under such note totals $1,227,388.67.

Convertible Promissory Note dated September 9, 2013 in the original principal amount of $579,766.10 issued to ProQuest Investments IV, L.P. by ZP Holdings, Inc. As of the Closing Date, the principal and interest outstanding under such note totals $613,694.33.

Convertible Promissory Note dated September 9, 2013 in the original principal amount of $5.30 issued to ProQuest Management LLC by ZP Holdings, Inc. As of the Closing Date, the principal and interest outstanding under such note totals $5.61.

Convertible Promissory Note dated February 26, 2014 in the original principal amount of $249,000 issued to BMV Direct SO LP by ZP Holdings, Inc. As of the Closing Date, the principal and interest outstanding under such note totals $254,293.81.

Convertible Promissory Note dated February 26, 2014 in the original principal amount of $1,069,709.23 issued to BMV Direct SOTRS LP by ZP Holdings, Inc. As of the Closing Date, the principal and interest outstanding under such note totals $1,092,451.54.

Convertible Promissory Note dated February 26, 2014 in the original principal amount of $1,181,290.77 issued to New Enterprise Associates 12, Limited Partnership by ZP Holdings, Inc. As of the Closing Date, the principal and interest outstanding under such note totals $1,206,405.34.

Schedule 1B

Existing Permitted Investments

100% stock ownership of Borrower (Zosano Pharma, Inc.), a Delaware corporation located at 34790 Ardentech Court, Fremont, CA 94555.

100% stock ownership of Zosano, Inc. (formerly named Eco Planet Corp.), a Delaware corporation located at 34790 Ardentech Court, Fremont, CA 94555.

Borrower holds 100% of the membership interests in ZP Group LLC, a Delaware limited liability company located at 34790 Ardentech Court, Fremont, CA 94555.

Schedule 1C

Existing Permitted Liens

Secured liens on all assets held by BioMed Realty Holdings, Inc. and BMV Direct SOTRS LP, which secured liens are subordinated to Lender’s Lien pursuant to the Subordination Agreement.

Schedule 5.14

Capitalization

ZP Holdings’ capitalization as of the Closing Date is as follows: 30,000,000 authorized shares of Common Stock, 20,427,250.579 of which are outstanding and held as follows:**

ZP Holdings has reserved 2,264,108 shares of Common Stock for issuance pursuant to the terms of its 2012 Stock Incentive Plan. Options to purchase 2,171,396 of such shares have been granted and are outstanding.

Pursuant to that certain Note Purchase Agreement dated as of September 9, 2013 by and among ZP Holdings and the purchasers named therein, ZP Holdings issued (and there are currently outstanding) Convertible Promissory Notes dated September 9, 2013 in the aggregate original principal amount of $3,033,723.04 (as set forth on Schedule 1A), which Convertible Promissory Notes automatically convert into equity securities of ZP Holdings upon the closing of a Qualified Financing as more fully described in such Note Purchase Agreement.

Pursuant to that certain Note Purchase Agreement dated as of February 26, 2014 by and among ZP Holdings and the purchasers named therein, ZP Holdings issued (and there are currently outstanding) Convertible Promissory Notes dated February 26, 2014 (as set forth in Schedule 1A) in the aggregate original principal amount of $2,500,000, which Convertible Promissory Notes automatically convert into equity securities of ZP Holdings upon the closing of a Qualified Financing as more fully described in such Note Purchase Agreement.

See Schedule 1 for list of Subsidiaries of ZP Holdings.

Schedule 7.9

Licenses

None.