FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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(Print or Type Responses)

1. Name and Address of Reporting Person * CASH HARVEY B   2. Issuer Name and Ticker or Trading Symbol METABASIS THERAPEUTICS INC [MBRX] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director __X__ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 13455 NOEL ROAD, SUITE 1670 3. Date of Earliest Transaction (Month/Day/Year) 05/16/2006 (Street) DALLAS, TX 75240 4. If Amendment, Date Original Filed(Month/Day/Year) 6. Individual or Joint/Group Filing(Check Applicable Line) _X_ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person (City) (State) (Zip) Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned

1.Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 05/16/2006   P   4,464 A $ 7.9987 4,464 I by InterWest Venture Mgmt Co. PSRP fbo Harvey B. Cash Common Stock 05/18/2006   P   700 A $ 8.1 5,164 I by InterWest Venture Mgmt Co. PSRP fbo Harvey B. Cash Common Stock 05/19/2006   P   5,000 A $ 8.1 10,164 I by InterWest Venture Mgmt Co. PSRP fbo Harvey B. Cash Common Stock 05/22/2006   P   39,836 A $ 8.0241 50,000 I by InterWest Venture Mgmt Co. PSRP fbo Harvey B. Cash

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 3)

2. Conversion or Exercise Price of Derivative Security

3. Transaction Date (Month/Day/Year)

3A. Deemed Execution Date, if any (Month/Day/Year)

4. Transaction Code (Instr. 8)

5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5)

6. Date Exercisable and Expiration Date (Month/Day/Year)

7. Title and Amount of Underlying Securities (Instr. 3 and 4)

8. Price of Derivative Security (Instr. 5)

9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)

10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4)

11. Nature of Indirect Beneficial Ownership (Instr. 4)

Code

V

(A)

(D)

Date Exercisable

Expiration Date

Title

Amount or Number of Shares

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
CASH HARVEY B 13455 NOEL ROAD SUITE 1670 DALLAS, TX 75240		X

Signatures

/s/ Harvey B. Cash		05/24/2006
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 4(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Remarks: Mr. Cash is a Managing Director of InterWest Management Partners VII, LLC, the general partner of InterWest Partners VII, LP, and InterWest Investors VII, LP ("the IW Funds"). The IW Funds own a total of 2,630,673 shares of Issuer's commom stock and warrants to purchase 555,625 shares of common stock. Mr. Cash disclaims beneficial ownership of the shares and warrants held by the IW Funds except to the extent of his pecuniary interest therein. Mr. Cash is deemed to be a 10% owner of the Issuer due to these indirect holdings by the IW Funds. With this filing, there is no change in the IW Funds' beneficial ownership of the Issuer.

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