sc13da407422007_05022011.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 2,696,302
	9	SOLE DISPOSITIVE POWER - 0 -
	10	SHARED DISPOSITIVE POWER 2,696,302
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,696,302
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES		o
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 3.3%
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 1,814,900
	9	SOLE DISPOSITIVE POWER - 0 -
	10	SHARED DISPOSITIVE POWER 1,814,900
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 1,814,900
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES		o
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 2.2%
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 6,982,615
	9	SOLE DISPOSITIVE POWER - 0 -
	10	SHARED DISPOSITIVE POWER 6,982,615
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 6,982,615
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES		o
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 8.5%
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 800,675
	9	SOLE DISPOSITIVE POWER - 0 -
	10	SHARED DISPOSITIVE POWER 800,675
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 800,675
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES		o
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) Less than 1%
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 12,304,492
	9	SOLE DISPOSITIVE POWER - 0 -
	10	SHARED DISPOSITIVE POWER 12,304,492
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 12,304,492
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES		o
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 14.98%
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 12,304,492
	9	SOLE DISPOSITIVE POWER - 0 -
	10	SHARED DISPOSITIVE POWER 12,304,492
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 12,304,492
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES		o
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 14.98%
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 12,304,492
	9	SOLE DISPOSITIVE POWER - 0 -
	10	SHARED DISPOSITIVE POWER 12,304,492
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 12,304,492
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES		o
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 14.98%
14	TYPE OF REPORTING PERSON IN

CUSIP NO. 15100E106

The following constitutes Amendment No. 4 to the Schedule 13D filed by the undersigned (“Amendment No. 4”). This Amendment No. 4 amends the Schedule 13D as specifically set forth herein.

Item 2.

Identity and Background.

(a) This statement is filed by Biotechnology Value Fund, L.P., a Delaware limited partnership (“BVF”), Biotechnology Value Fund II, L.P., a Delaware limited partnership (“BVF2”), BVF Investments, L.L.C., a Delaware limited liability company (“BVLLC”), Investment 10, L.L.C., an Illinois limited liability company (“ILL10”), BVF X LLC, a Delaware limited liability company (“BVFX”), BVF Partners L.P., a Delaware limited partnership (“Partners”), BVF Inc., a Delaware corporation, and Mark N. Lampert. Mr. Lampert is the sole shareholder, sole director and an officer of BVF Inc.

Each of the foregoing is referred to as a “Reporting Person” and collectively as the “Reporting Persons.” Each of the Reporting Persons is party to that certain Joint Filing Agreement, as further described in Item 6. Accordingly, the Reporting Persons are hereby filing a joint Schedule 13D.

(b) The business address of BVF, BVF2, BVLLC, ILL10, BVFX, Partners, BVF Inc. and Mr. Lampert is 900 North Michigan Avenue, Suite 1100, Chicago, Illinois 60611.

(c) Each of BVF, BVF2, BVLLC, ILL10 and BVFX specializes in holding biotechnology stocks for investment purposes. Partners is the general partner of BVF and BVF2, which are investment funds. Partners is the manager of BVLLC, which is an investment fund. ILL10 is a managed account, which Partners advises pursuant to an investment management agreement. BVF, BVF2, BVLLC and ILL10 are members of BVFX. BVF Inc. is the investment adviser to and general partner of Partners. Mr. Lampert is the sole shareholder, sole director and an officer of BVF Inc.

(d) During the last five years, none of the Reporting Persons has been convicted in a criminal proceeding (excluding traffic violations and similar misdemeanors).

(e) During the last five years, none of the Reporting Persons has been a party to a civil proceeding of a judicial or administrative body of competent jurisdiction nor, as a result of such proceeding, was or is subject to a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violation with respect to such laws.

(f) Mr. Lampert is a citizen of the United States of America.

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 12,304,492 Shares beneficially owned in the aggregate by BVF, BVF2, BVLLC, ILL10 and BVFX is approximately $89,654,709, including brokerage commissions.

CUSIP NO. 15100E106

Item 4.

Purpose of Transaction

Item 4 is hereby amended to add the following:

As stated previously, the Reporting Persons intend to pursue all available options in order to realize the fair value of their investment in the Issuer. Accordingly, on May 2, 2011, the Reporting Persons filed a Notice of Intention to Object to the proposed settlement (the “Settlement”) of previously consolidated class action lawsuits filed in Delaware and California state courts relating to the agreement by Quest Diagnostics Incorporated (“Quest”) to acquire the Issuer.

On March 18, 2011, the Issuer announced that it had entered into an agreement and plan of merger (the “Merger”) with Quest and Spark Acquisition Corporation, a wholly owned subsidiary of Quest (the “Purchaser”), pursuant to which the Purchaser commenced a tender offer (the “Tender Offer”) to acquire all of the issued and outstanding Shares for $8.00 per Share. Shortly thereafter, multiple class action lawsuits objecting to the Merger were filed against the Issuer and its board of directors. On April 1, 2011, three such lawsuits were consolidated into a single action and the New Orleans Employees’ Retirement System (“NOERS”) was appointed the lead plaintiff. On April 1, 2011, a Verified Consolidated Amended Class Action Complaint was filed by NOERS in the consolidated action. On April 18, 2011, the parties to the consolidated action entered into a memorandum of understanding with Quest, the Purchaser and the Issuer, regarding the Settlement.

On May 2, 2011, Partners filed a Notice of Intention to Object to Proposed Settlement, a copy of which is attached as Exhibit 99.1 hereto.

On May 4, 2011, Quest announced the successful completion of the Tender Offer.

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 3, 2011, BVF beneficially owned 2,696,302 Shares, BVF2 beneficially owned 1,814,900 Shares, BVLLC beneficially owned 6,982,615 Shares, ILL10 beneficially owned 800,675 Shares and BVFX beneficially owned 10,000 Shares, representing percentage ownership of approximately 3.3%, 2.2%, 8.5%, less than 1% and less than 1%, respectively, of the Shares outstanding.

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 12,304,492 Shares beneficially owned in the aggregate by BVF, BVF2, BVLLC, ILL10 and BVFX, representing percentage ownership of approximately 14.98% of the Shares outstanding. As the investment adviser and general partner of Partners, BVF Inc. may be deemed to beneficially own the 12,304,492 Shares beneficially owned by Partners, representing percentage ownership of approximately 14.98% of the Shares outstanding.

CUSIP NO. 15100E106

Mr. Lampert, as a director and officer of BVF Inc. may be deemed to beneficially own the 12,304,492 Shares beneficially owned by BVF Inc., representing percentage ownership of approximately 14.98% 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 12,304,492 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) On May 2, 2011, BVFX acquired 10,000 Shares for $7.9089 per Share. There have been no additional transactions in the securities of the Issuer since the filing of Amendment No. 3 to the Schedule 13D.

Item 6.

Contracts, Arrangements, Understandings or Relationships With Respect to Securities of the Issuer.

Item 6 is hereby amended to add the following:

On May 4, 2011, the Reporting Persons entered into a Joint Filing Agreement in which the Reporting Persons agreed to the joint filing on behalf of each of them of statements on Schedule 13D, with respect to securities of the Issuer, to the extent required by applicable law. A copy of this agreement is attached hereto as Exhibit 99.2 hereto and is incorporated herein by reference.

Item 7.

Material to be Filed as Exhibits.

Item 7 is hereby amended to add the following exhibits:

99.1

Notice of Intention to Object to Proposed Settlement, dated May 2, 2011.

99.2

Joint Filing Agreement by and among Biotechnology Value Fund, L.P., Biotechnology Value Fund II, L.P., BVF Investments, L.L.C., Investment 10, L.L.C., BVF X LLC, BVF Partners L.P., BVF Inc. and Mark N. Lampert, dated May 4, 2011.

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 4, 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