Ownership Submission
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
OMB APPROVAL
OMB Number: 3235-0287
Expires: January 31, 2005
Estimated average burden hours per response... 0.5

(Print or Type Responses)
1. Name and Address of Reporting Person *
Erion Mark D
  2. Issuer Name and Ticker or Trading Symbol
METABASIS THERAPEUTICS INC [MBRX]
5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
_____ Director _____ 10% Owner
__X__ Officer (give title below) _____ Other (specify below)
Chief Executive Officer
(Last)
(First)
(Middle)
11119 NORTH TORREY PINES ROAD
3. Date of Earliest Transaction (Month/Day/Year)
01/29/2009
(Street)

LA JOLLA, CA 92037
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

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB control number. SEC 1474 (9-02)

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
Stock Option (Right to Buy) $ 9.03 01/29/2009   D     75,000   (1) 03/19/2016 Common Stock 75,000 (2) 0 D  
Stock Option (Right to Buy) $ 7.55 01/29/2009   D     75,000   (3) 03/07/2017 Common Stock 75,000 (2) 0 D  
Stock Option (Right to Buy) $ 2.1 01/29/2009   D     90,000   (4) 04/02/2018 Common Stock 90,000 (2) 0 D  
Stock Option (Right to Buy) $ 1 01/29/2009   D   240,000     (5) 01/29/2019 Common Stock 240,000 (2) 240,000 D  

Reporting Owners

Reporting Owner Name / Address Relationships
 Director  10% Owner  Officer  Other
Erion Mark D
11119 NORTH TORREY PINES ROAD
LA JOLLA, CA 92037
      Chief Executive Officer  

Signatures

 Trisha Millican, by Power of Attorney   02/02/2009
**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).
(1) The cancelled option provided for 25% of the shares vesting on the first anniversary of the grant date (3/19/2006), and the remaining shares vesting in equal monthly installments over the following three years.
(2) Pursuant to the Company's Offer to Exchange Stock Options, on January 29, 2009, the Company cancelled options granted to the reporting person in exchange for new options equal to the number of shares under the cancelled options.
(3) The cancelled option provided for 25% of the shares vesting on the first anniversary of the grant date (3/7/2007), and the remaining shares vesting in equal monthly installments over the following three years.
(4) The cancelled option provided for 25% of the shares vesting on the first anniversary of the grant date (4/2/2008), and the remaining shares vesting in equal monthly installments over the following three years.
(5) The option provides for 25% of the shares to vest six months from the grant date (1/29/09) and the remaining 75% of the shares to vest in equal monthly installments over three years beginning on the grant date.

Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.

Potential persons who are to respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB number.