sc13da507422007_05042011.htm

CUSIP NO. 15100E106

1	NAME OF REPORTING PERSON BIOTECHNOLOGY VALUE FUND, L.P.
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP		(a) x (b) o
3	SEC USE ONLY
4	SOURCE OF FUNDS WC
5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(d) OR 2(e)		¨
6	CITIZENSHIP OR PLACE OF ORGANIZATION DELAWARE
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	7	SOLE VOTING POWER - 0 -
	8	SHARED VOTING POWER 3,351,702
	9	SOLE DISPOSITIVE POWER - 0 -
	10	SHARED DISPOSITIVE POWER 3,351,702
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 3,351,702
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES		o
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 4.1%
14	TYPE OF REPORTING PERSON PN

CUSIP NO. 15100E106

1	NAME OF REPORTING PERSON BIOTECHNOLOGY VALUE FUND II, L.P.
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP		(a) x (b) o
3	SEC USE ONLY
4	SOURCE OF FUNDS WC
5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(d) OR 2(e)		¨
6	CITIZENSHIP OR PLACE OF ORGANIZATION DELAWARE
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	7	SOLE VOTING POWER - 0 -
	8	SHARED VOTING POWER 2,268,900
	9	SOLE DISPOSITIVE POWER - 0 -
	10	SHARED DISPOSITIVE POWER 2,268,900
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,268,900
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES		o
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 2.8%
14	TYPE OF REPORTING PERSON PN

CUSIP NO. 15100E106

1	NAME OF REPORTING PERSON BVF INVESTMENTS, L.L.C.
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP		(a) x (b) o
3	SEC USE ONLY
4	SOURCE OF FUNDS WC
5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(d) OR 2(e)		¨
6	CITIZENSHIP OR PLACE OF ORGANIZATION DELAWARE
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	7	SOLE VOTING POWER - 0 -
	8	SHARED VOTING POWER 8,554,615
	9	SOLE DISPOSITIVE POWER - 0 -
	10	SHARED DISPOSITIVE POWER 8,554,615
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 8,554,615
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES		o
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 10.4%
14	TYPE OF REPORTING PERSON OO

CUSIP NO. 15100E106

1	NAME OF REPORTING PERSON INVESTMENT 10, L.L.C.
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP		(a) x (b) o
3	SEC USE ONLY
4	SOURCE OF FUNDS WC
5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(d) OR 2(e)		¨
6	CITIZENSHIP OR PLACE OF ORGANIZATION ILLINOIS
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	7	SOLE VOTING POWER - 0 -
	8	SHARED VOTING POWER 963,675
	9	SOLE DISPOSITIVE POWER - 0 -
	10	SHARED DISPOSITIVE POWER 963,675
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 963,675
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES		o
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 1.2%
14	TYPE OF REPORTING PERSON OO

CUSIP NO. 15100E106

1	NAME OF REPORTING PERSON BVF X LLC
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP		(a) x (b) o
3	SEC USE ONLY
4	SOURCE OF FUNDS WC
5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(d) OR 2(e)		¨
6	CITIZENSHIP OR PLACE OF ORGANIZATION DELAWARE
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	7	SOLE VOTING POWER - 0 -
	8	SHARED VOTING POWER 10,000
	9	SOLE DISPOSITIVE POWER - 0 -
	10	SHARED DISPOSITIVE POWER 10,000
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 10,000
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES		o
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) Less than 1%
14	TYPE OF REPORTING PERSON OO

CUSIP NO. 15100E106

1	NAME OF REPORTING PERSON BVF PARTNERS L.P.
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP		(a) x (b) o
3	SEC USE ONLY
4	SOURCE OF FUNDS AF
5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(d) OR 2(e)		¨
6	CITIZENSHIP OR PLACE OF ORGANIZATION DELAWARE
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	7	SOLE VOTING POWER - 0 -
	8	SHARED VOTING POWER 15,148,892
	9	SOLE DISPOSITIVE POWER - 0 -
	10	SHARED DISPOSITIVE POWER 15,148,892
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 15,148,892
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES		o
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 18.4%
14	TYPE OF REPORTING PERSON PN, IA

CUSIP NO. 15100E106

1	NAME OF REPORTING PERSON BVF INC.
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP		(a) x (b) o
3	SEC USE ONLY
4	SOURCE OF FUNDS AF
5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(d) OR 2(e)		¨
6	CITIZENSHIP OR PLACE OF ORGANIZATION DELAWARE
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	7	SOLE VOTING POWER - 0 -
	8	SHARED VOTING POWER 15,148,892
	9	SOLE DISPOSITIVE POWER - 0 -
	10	SHARED DISPOSITIVE POWER 15,148,892
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 15,148,892
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES		o
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 18.4%
14	TYPE OF REPORTING PERSON CO

CUSIP NO. 15100E106

1	NAME OF REPORTING PERSON MARK N. LAMPERT
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP		(a) x (b) o
3	SEC USE ONLY
4	SOURCE OF FUNDS AF
5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(d) OR 2(e)		¨
6	CITIZENSHIP OR PLACE OF ORGANIZATION USA
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	7	SOLE VOTING POWER - 0 -
	8	SHARED VOTING POWER 15,148,892
	9	SOLE DISPOSITIVE POWER - 0 -
	10	SHARED DISPOSITIVE POWER 15,148,892
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 15,148,892
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES		o
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 18.4%
14	TYPE OF REPORTING PERSON IN

CUSIP NO. 15100E106

The following constitutes Amendment No. 5 to the Schedule 13D filed by the undersigned (“Amendment No. 5”). This Amendment No. 5 amends the Schedule 13D as specifically set forth herein.

Item 3.

Source and Amount of Funds or Other Consideration.

Item 3 is hereby amended and restated to read as follows:

The Shares purchased by BVF, BVF2, BVLLC, ILL10 and BVFX were purchased with working capital (which may, at any given time, include margin loans made by brokerage firms in the ordinary course of business) in open market purchases. The aggregate purchase cost of the 15,148,892 Shares beneficially owned in the aggregate by BVF, BVF2, BVLLC, ILL10 and BVFX is approximately $112,635,491, including brokerage commissions.

Item 4.

Purpose of Transaction

Item 4 is hereby amended to add the following:

In connection with the completion of the tender offer by Quest Diagnostics Incorporated (“Quest”) for all of the issued and outstanding Shares for $8.00 per Share (the “Tender Offer”), the Reporting Persons are currently considering all of their available options with respect to their Shares including, among other options, exercising their appraisal rights in connection with the merger of the Issuer with a subsidiary of Quest (the “Merger”) and/or pursuing a claim for breach of fiduciary duty in connection with the Tender Offer and Merger. As previously disclosed, on May 2, 2011 BVF Partners L.P. filed a Notice of Intention to Object to Proposed Settlement with respect to the proposed settlement of the previously consolidated class action lawsuits filed in Delaware and California state courts relating to the agreement by Quest to acquire the Issuer (the “Lawsuit”), and currently intends to pursue the claims asserted in the Verified Consolidated Amended Class Action Complaint filed with respect to the Lawsuit, as well as other claims the Reporting Persons are investigating. The Reporting Persons also may endeavor to increase their position in the Issuer through, among other things, the purchase of Shares on the open market or in private transactions or otherwise, on such terms and at such times as the Reporting Persons may deem advisable.

There is no guarantee that the Reporting Persons will pursue any of the aforementioned actions and/or that any such actions will benefit other stockholders. The Reporting Persons reserve the right to change their intention with respect to any and all matters referred to in this Item 4 at any time.

Item 5.

Interest in Securities of the Issuer.

Items 5(a) and (b) are hereby amended and restated to read as follows:

(a) The aggregate percentage of Shares reported owned by each person named herein is based upon 82,155,471 Shares outstanding, which is the total number of Shares outstanding as of March 16, 2011, as reported in the Issuer’s Recommendation Statement on Schedule 14D-9 filed with the Securities and Exchange Commission on March 28, 2011.

As of the close of business on May 5, 2011, BVF beneficially owned 3,351,702 Shares, BVF2 beneficially owned 2,268,900 Shares, BVLLC beneficially owned 8,554,615 Shares, ILL10 beneficially owned 963,675 Shares and BVFX beneficially owned 10,000 Shares, representing percentage ownership of approximately 4.1%, 2.8%, 10.4%, 1.2% and less than 1%, respectively, of the Shares outstanding.

CUSIP NO. 15100E106

As the general partner of BVF and BVF2, the manager of BVLLC, the investment adviser of ILL10 and the general partner, manager and investment adviser, as the case may be, of the members of BVFX, Partners may be deemed to beneficially own the 15,148,892 Shares beneficially owned in the aggregate by BVF, BVF2, BVLLC, ILL10 and BVFX, representing percentage ownership of approximately 18.4% of the Shares outstanding. As the investment adviser and general partner of Partners, BVF Inc. may be deemed to beneficially own the 15,148,892 Shares beneficially owned by Partners, representing percentage ownership of approximately 18.4% of the Shares outstanding.

Mr. Lampert, as a director and officer of BVF Inc. may be deemed to beneficially own the 15,148,892 Shares beneficially owned by BVF Inc., representing percentage ownership of approximately 18.4% of the Shares outstanding.

(b) Each of BVF, BVF2, BVLLC, ILL10 and BVFX shares with Partners voting and dispositive power over the Shares each such entity beneficially owns. Partners, BVF Inc. and Mr. Lampert share voting and dispositive power over the 15,148,892 Shares they may be deemed to beneficially own with BVF, BVF2, BVLLC, ILL10 and BVFX.

Item 5(c) is hereby amended to add the following:

(c) Schedule A annexed hereto lists all transactions in securities of the Issuer since the filing of Amendment No. 4 to the Schedule 13D. All of such transactions were effected in the open market.

CUSIP NO. 15100E106

SIGNATURES

After reasonable inquiry and to the best of his knowledge and belief, each of the undersigned certifies that the information set forth in this statement is true, complete and correct.

Dated: May 6, 2011

BIOTECHNOLOGY VALUE FUND, L.P.		INVESTMENT 10, L.L.C.

By:	BVF Partners L.P., its general partner	By:	BVF Partners L.P., its investment manager

By:	BVF Inc., its general partner	By:	BVF Inc., its general partner

By:	/s/ Mark N. Lampert	By:	/s/ Mark N. Lampert
	Mark N. Lampert		Mark N. Lampert
	President		President

BIOTECHNOLOGY VALUE FUND II, L.P.		BVF X LLC

By:	BVF Partners L.P., its general partner	By:	Biotechnology Value Fund, L.P., member

By:	BVF Inc., its general partner	By:	BVF Partners L.P., its general partner

By:	/s/ Mark N. Lampert	By:	BVF Inc., its general partner
	Mark N. Lampert
	President	By:	/s/ Mark N. Lampert
			Mark N. Lampert
			President

BVF INVESTMENTS, L.L.C.		BVF PARTNERS L.P.

By:	BVF Partners L.P., its manager	By:	BVF Inc., its general partner

By:	BVF Inc., its general partner	By:	/s/ Mark N. Lampert
			Mark N. Lampert
By:	/s/ Mark N. Lampert		President
	Mark N. Lampert
	President

	BVF INC.

/s/ Mark N. Lampert	By:	/s/ Mark N. Lampert
MARK N. LAMPERT		Mark N. Lampert
		President

CUSIP NO. 15100E106

SCHEDULE A

Transactions in the Securities of the Issuer Since the Filing of Amendment No. 4 to the Schedule 13D

Class of Security	Securities Purchased	Price ($)	Date of Purchase
BIOTECHNOLOGY VALUE FUND, L.P.
Common Stock	548,000	8.0499	05/04/11
Common Stock	107,400	8.0463	05/05/11
BIOTECHNOLOGY VALUE FUND II, L.P.
Common Stock	379,000	8.0499	05/04/11
Common Stock	75,000	8.0463	05/05/11
INVESTMENT 10, L.L.C.
Common Stock	136,000	8.0499	05/04/11
Common Stock	27,000	8.0463	05/05/11
BVF INVESTMENTS, L.L.C.
Common Stock	1,313,000	8.0499	05/04/11
Common Stock	259,000	8.0463	05/05/11