Metabasis Therapeutics, Inc.

(Name of Issuer)

Common Stock, par value $0.001 per share

(Title of Class of Securities)

59101M 10 5

(CUSIP Number)

November 1, 2006

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

o Rule 13d-1(b)

x Rule 13d-1(c)

o Rule 13d-1(d)

*The remainder of this cover page shall be filled out for a reporting person’s initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter the disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

1

NAMES OF REPORTING PERSONS
I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (entities only)

Credit Suisse, on behalf of the Investment Banking division

2

CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

(a)

(b)

X

3

SEC USE ONLY

4

CITIZENSHIP OR PLACE OF ORGANIZATION

SWITZERLAND

NUMBER OF

SHARES
BENEFICIALLY
OWNED BY
EACH

REPORTING
PERSON
WITH

5

SOLE VOTING POWER

-0-

6

SHARED VOTING POWER

3,915,680

7

SOLE DISPOSITIVE POWER

-0-

8

SHARED DISPOSITIVE POWER

3,915,680

9

AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

3,915,680

10

CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES   o

11

PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

12.7%

12

TYPE OF REPORTING PERSON

BK

2

Item 1.

(a)

Name of Issuer:

Metabasis Therapeutics, Inc.

(b)

Address of Issuer’s Principal Executive Offices:

11119 North Torrey Pines Road, La Jolla, CA 92037

Item 2.

(a)

Name of Person Filing:

Credit Suisse, on behalf of the Investment Banking division. See Schedule I.

(b)

Address of Principal Business Office or, if none, residence:

Uetlibergstrasse 231, P.O. Box 900, CH-8070 Zurich, Switzerland

(c)

Citizenship:

Switzerland

(d)

Title of Class of Securities:

Common Stock, par value $0.001 per share

(e)

CUSIP Number:

59101M 10 5

Item 3.

If this statement is filed pursuant to §§ 240.13d-1(b), or 240.13d-2(b) or (c), check whether the person filing is a:

(a)

Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o)

(b)

Bank as defined in Section 3(a)(6) of the Act (15 U.S.C. 78c)

(c)

Insurance company as defined in Section 3(a)(19) of the Act (15 U.S.C. 78c)

(d)

Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8)

(e)

An investment adviser in accordance with §240.13d-1(b)(1)(ii)(E)

(f)

An employee benefit plan or endowment fund in accordance with §240.13d-1(b)(1)(ii)(F)

(g)

A parent holding company or control person in accordance with §240.13d-1(b)(1)(ii)(G)

(h)

A savings association as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813)

(i)

A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3)

(j)

Group, in accordance with §240.13d-1(b)(1)(ii)(J)

3

Item 4.

Ownership

(a)

Amount Beneficially Owned:

See response to Item 9 on page 2.

      (b)

Percent of Class:

See response to Item 11 on page 2.

(c)

Number of shares as to which such person has:

(i)

Sole power to vote or to direct the vote:

See response to Item 5 on page 2.

(ii)

Shared power to vote or to direct the vote:

See response to Item 6 on page 2.

(iii)

Sole power to dispose or to direct the disposition of:

See response to Item 7 on page 2.

(iv)

Shared power to direct the disposition of:

See response to Item 8 on page 2.

Item 5.

Ownership of Five Percent or Less of a Class

o

Item 6.

Ownership of More than Five Percent on Behalf of Another Person

Not applicable

Item 7.

Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on By the Parent Holding Company

See Schedule I.

Item 8.

Identification and Classification of Members of the Group

Not applicable

Item 9.

Notice of Dissolution of Group

Not Applicable

Item 10.

Certification

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect.

4

5

6