SC TO-T/A

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE TO

TENDER OFFER STATEMENT UNDER SECTION 14(d)(1) OR 13(e)(1) OF THE

SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 16)

Allos Therapeutics, Inc.

(Name of Subject Company (Issuer))

Sapphire Acquisition Sub, Inc.

(Offeror)

a wholly owned subsidiary of

Spectrum Pharmaceuticals, Inc.

(Parent of Offeror)

COMMON STOCK, $0.001 PAR VALUE PER SHARE

(Title of Class of Securities)

019777101

(CUSIP Number of Class of Securities)

Rajesh C. Shrotriya, M.D.

Spectrum Pharmaceuticals, Inc.

11500 South Eastern Ave., Suite 240

Henderson, Nevada 89052

(702) 835-6300

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications

on Behalf of Filing Persons)

Copies to:

R. Scott Falk, Esq. Kirkland & Ellis LLP 300 North LaSalle Street Chicago, Illinois 60654 (312) 862-2200 Eva H. Davis, Esq. Kirkland & Ellis LLP 333 South Hope Street Los Angeles, California 90071 (213) 680-8400

CALCULATION OF FILING FEE

Transaction Valuation(1)	Amount of Filing Fee(2)
$218,545,445.26	$25,043.31

(1) Estimated for purposes of calculating the filing fee only. The calculation assumes the purchase of 113,235,982 shares of Allos Therapeutics, Inc. common stock (assuming full vesting and settlement in common stock of issued and outstanding restricted stock unit awards and exercise of issued and outstanding stock options with an exercise price of less than $1.82) at a price of $1.93 per share.

(2) Calculated in accordance with Rule 0-11 under the Securities and Exchange Act of 1934, as amended, and Fee Rate Advisory #3 for fiscal year 2012, issued September 29, 2011, by multiplying the transaction value by 0.0001146.

þ Check the box if any part of the fee is offset as provided by Rule 0-11(a)(2) and identify the filing with which the offsetting fee was previously paid. Identify the previous filing by registration statement number, or the Form or Schedule and the date of its filing.

¨ Check the box if the filing relates solely to preliminary communications made before the commencement of a tender offer.

Amount Previously Paid:	$25,043.31	Filing Party:	Spectrum Pharmaceuticals, Inc.
Form or Registration No.:	Schedule TO	Date Filed:	April 16, 2012

Check the appropriate boxes below to designate any transactions to which the statement relates:

þ Third-party offer subject to Rule 14d-1.

¨ Issuer tender offer subject to Rule 13e-4.

¨ Going-private transactions subject to Rule 13e-3.

¨ Amendment to Schedule 13D under Rule 13d-2.

Check the following box if the filing is a final amendment reporting the results of the tender offer: ¨

This Amendment No. 16 amends and supplements the Tender Offer Statement on Schedule TO (which, together with any amendments and supplements thereto, collectively constitute this “Schedule TO”) relating to the tender offer by Sapphire Acquisition Sub, Inc., a Delaware corporation (the “Purchaser”), a wholly owned subsidiary of Spectrum Pharmaceuticals, Inc., a Delaware corporation (“Parent”), to purchase all of the outstanding shares of common stock, par value $0.001 per share (the “Shares”), of Allos Therapeutics, Inc., a Delaware corporation (“Allos”), at a price of $1.82 per share, net to the seller in cash, without interest thereon and less any applicable withholding taxes, plus one contingent value right (which, as described in Amendment No. 10 to this Schedule TO, has been determined to be without value), upon the terms and subject to the conditions set forth in the offer to purchase dated April 13, 2012 (the “Offer to Purchase”), a copy of which is attached as Exhibit (a)(1)(A), and in the related letter of transmittal (the “Letter of Transmittal”), a copy of which is attached as Exhibit (a)(1)(B), which, together with any amendments or supplements, collectively constitute the “Offer.”

All of the information set forth in the Offer to Purchase is incorporated by reference herein in response to Items 1 through 9 and Item 11 of this Schedule TO, and is supplemented by the information specifically provided for in this Schedule TO.

Item 11. Additional Information

Item 11 of the Schedule TO, and the Offer to Purchase, to the extent incorporated by reference therein, are hereby amended and supplemented as set forth below:

The following is inserted as the third paragraph in the subsection captioned “United States Antitrust Compliance” in Section 16—”Certain Legal Matters; Regulatory Approvals”:

“On August 28, 2012, the FTC terminated the waiting period under the HSR Act.”

Item 12. Exhibits

Item 12 of the Schedule TO is hereby amended and supplemented by adding the following exhibit:

Exhibit No.	Description
(a)(1)(W)	Joint Press Release issued August 28, 2012

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SIGNATURES

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

Dated: August 28, 2012

SAPPHIRE ACQUISITION SUB, INC.
By:	/s/ Brett L. Scott
Name:	Brett L. Scott
Title:	Chief Financial Officer
SPECTRUM PHARMACEUTICALS, INC.
By:	/s/ Brett L. Scott
Name:	Brett L. Scott
Title:	Senior Vice President and Acting Chief Financial Officer

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Exhibit Index

Exhibit No.		Description
	(a)(1)(A)	Offer to Purchase, dated April 13, 2012*
	(a)(1)(B)	Form of Letter of Transmittal*
	(a)(1)(C)	Form of Notice of Guaranteed Delivery*
	(a)(1)(D)	Form of Letter to Brokers, Dealers, Commercial Banks, Trust Companies and Other Nominees*
	(a)(1)(E)	Form of Letter to Clients for use by Brokers, Dealers, Commercial Banks, Trust Companies and Other Nominees*
	(a)(1)(F)	Form of Summary Advertisement as published on April 13, 2012 in the New York Times*
	(a)(1)(G)	Joint Press Release issued April 5, 2012 (incorporated by reference to Exhibit 99.1 to the Current Report of Form 8-K filed by Spectrum Pharmaceuticals, Inc. with the Securities and Exchange Commission on April 5, 2012)*
	(a)(1)(H)	Complaint filed in the United States District Court for the District of Colorado, captioned Radmore v. Allos Therapeutics, Inc., et al. (incorporated by reference to Exhibit (g)(1) to the Schedule 14D-9 filed by Allos Therapeutics, Inc. with the Securities and Exchange Commission on April 16, 2012)*
	(a)(1)(I)	Complaint filed in the Court of Chancery of the State of Delaware, captioned Keucher v. Berns et al. (incorporated by reference to Exhibit (g)(2) to the Schedule 14D-9 filed by Allos Therapeutics, Inc. with the Securities and Exchange Commission on April 16, 2012)*
	(a)(1)(J)	Press Release issued by Spectrum Pharmaceuticals, Inc. on April 16, 2012*
	(a)(1)(K)	Amended Complaint, filed in the Court of Chancery of the State of Delaware, captioned Keucher v. Berns et al. (incorporated by reference to Exhibit (g)(3) to Amendment No. 2 to the Schedule 14D-9 filed by Allos Therapeutics, Inc. with the Securities and Exchange Commission on April 24, 2012)*
	(a)(1)(L)	Second Amended Class Complaint, filed in the Court of Chancery of the State of Delaware, captioned In re Allos Therapeutics, Inc. Shareholders Litigation (incorporated by reference to Exhibit (g)(4) to Amendment No. 2 to the Schedule 14D-9 filed by Allos Therapeutics, Inc. with the Securities and Exchange Commission on April 24, 2012)*
	(a)(1)(M)	Amended Complaint, filed in the United States District Court for the District of Colorado, captioned Radmore v. Allos Therapeutics, Inc. et al. (incorporated by reference to Exhibit (g)(5) to Amendment No. 3 to the Schedule 14D-9 filed by Allos Therapeutics, Inc. with the Securities and Exchange Commission on May 1, 2012)*
	(a)(1)(N)	Memorandum of Understanding, dated as of May 3, 2012*
	(a)(1)(O)	Joint Press Release issued May 10, 2012 (incorporated by reference to Exhibit (a)(5) to Amendment No. 5 to the Schedule 14D-9 filed by Allos Therapeutics, Inc. with the Securities and Exchange Commission on May 10, 2012)*
	(a)(1)(P)	Joint Press Release issued May 24, 2012 (incorporated by reference to Exhibit (a)(6) to Amendment No. 6 to the Schedule 14D-9 filed by Allos Therapeutics, Inc. with the Securities and Exchange Commission on May 25, 2012)*
	(a)(1)(Q)	Joint Press Release issued June 7, 2012 (incorporated by reference to Exhibit (a)(7) to Amendment No. 7 to the Schedule 14D-9 filed by Allos Therapeutics, Inc. with the Securities and Exchange Commission on June 8, 2012)*
	(a)(1)(R)	Joint Press Release issued June 21, 2012 (incorporated by reference to Exhibit (a)(8) to Amendment No. 8 to the Schedule 14D-9 filed by Allos Therapeutics, Inc. with the Securities and Exchange Commission on June 22, 2012)*
	(a)(1)(S)	Joint Press Release issued July 6, 2012 (incorporated by reference to Exhibit (a)(9) to Amendment No. 10 to the Schedule 14D-9 filed by Allos Therapeutics, Inc. with the Securities and Exchange Commission on July 9, 2012)*
	(a)(1)(T)	Joint Press Release issued July 20, 2012 (incorporated by reference to Exhibit (a)(10) to Amendment No. 11 to the Schedule 14D-9 filed by Allos Therapeutics, Inc. with the Securities and Exchange Commission on July 23, 2012)*

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Exhibit No.		Description
	(a)(1)(U)	Joint Press Release issued August 3, 2012 (incorporated by reference to Exhibit (a)(11) to Amendment No. 12 to the Schedule 14D-9 filed by Allos Therapeutics, Inc. with the Securities and Exchange Commission on August 6, 2012)*
	(a)(1)(V)	Joint Press Release issued August 17, 2012 (incorporated by reference to Exhibit (a)(12) to Amendment No. 13 to the Schedule 14D-9 filed by Allos Therapeutics, Inc. with the Securities and Exchange Commission on August 20, 2012)*
	(a)(1)(W)	Joint Press Release issued August 28, 2012
	(d)(1)	Agreement and Plan of Merger, dated as of April 4, 2012, among Spectrum Pharmaceuticals, Inc., Sapphire Acquisition Sub, Inc. and Allos Therapeutics, Inc. (incorporated by reference to Exhibit 2.1 to the Current Report on Form 8-K filed by Spectrum Pharmaceuticals, Inc. with the Securities and Exchange Commission on April 5, 2012)*
	(d)(2)	Form of Contingent Value Rights Agreement to be entered into by and among the Allos Therapeutics, Inc., Spectrum Pharmaceuticals, Inc. and a Rights Agent to be designated (incorporated by reference to Exhibit 2.2 to the Current Report on Form 8-K filed by Spectrum Pharmaceuticals, Inc. with the Securities and Exchange Commission on April 5, 2012)*
	(d)(3)	Form of Voting and Tender Agreement among Spectrum Pharmaceuticals, Inc., Sapphire Acquisition Sub, Inc. and the stockholders set forth therein (incorporated by reference to Exhibit 2.3 to the Current Report on Form 8-K filed by Spectrum Pharmaceuticals, Inc. with the Securities and Exchange Commission on April 5, 2012)*
	(d)(4)	Commitment Letter, dated as of April 4, 2012, among Spectrum Pharmaceuticals, Inc., Bank of America, N.A. and Merrill Lynch, Pierce, Fenner & Smith Incorporated*
	(d)(5)	Confidentiality Agreement, dated as of September 23, 2011, by and among Allos Therapeutics, Inc. and Spectrum Pharmaceuticals, Inc. (incorporated by reference to Exhibit (e)(4) to the Schedule 14D-9 filed by Allos Therapeutics, Inc. with the Securities and Exchange Commission on April 16, 2012)*
	(d)(6)	Letter Agreement, dated as of March 19, 2012, between Allos Therapeutics, Inc. and Spectrum Pharmaceuticals, Inc. (incorporated by reference to Exhibit (e)(5) to the Schedule 14D-9 filed by Allos Therapeutics, Inc. with the Securities and Exchange Commission on April 16, 2012)*
	(d)(7)	Letter Agreement, dated as of March 30, 2012, between Allos Therapeutics, Inc. and Spectrum Pharmaceuticals, Inc. (incorporated by reference to Exhibit (e)(6) to the Schedule 14D-9 filed by Allos Therapeutics, Inc. with the Securities and Exchange Commission on April 16, 2012)*
	(a)(5)(A)	Allos Employee Frequently Asked Questions distributed to Allos employees on August 23, 2012 (incorporated by reference to Exhibit (a)(13) to Amendment No. 14 to the Schedule 14D-9 filed by Allos Therapeutics, Inc. with the Securities and Exchange Commission on August 23, 2012)*

* Previously filed.

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EX-99.(A)(1)(W)

Exhibit (a)(1)(w)

Spectrum Pharmaceuticals and Allos Therapeutics Announce That FTC Clears Transaction;

Tender Offer for Shares of Allos Common Stock To Expire

at 5pm Eastern Time on September 4, 2012

• Spectrum intends to accept for payment shares of Allos common stock on September 4, 2012

HENDERSON, Nev. and WESTMINSTER, Colo. – August 28, 2012 – Spectrum Pharmaceuticals, Inc. (NasdaqGS: SPPI) (Spectrum) and Allos Therapeutics, Inc. (NasdaqGS: ALTH) (Allos) today announced that the Federal Trade Commission terminated the waiting period under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended, relating to the previously announced pending acquisition of all outstanding shares of common stock of Allos by Spectrum.

As previously disclosed, Spectrum has commenced a tender offer to purchase all of the outstanding shares of common stock of Allos for $1.82 per share in cash, without interest and less any applicable withholding taxes.

Spectrum intends to accept for payment shares of Allos common stock validly tendered and not withdrawn prior to the scheduled tender offer expiration at 5:00 p.m., Eastern time, on Tuesday, September 4, 2012. The consummation of the tender offer is conditioned upon the tender of a majority of the outstanding shares of Allos common stock, as well as other conditions that are specified in the Schedule TO filed with the Securities and Exchange Commission on April 13, 2012.

“This acquisition is a transformational step for Spectrum, building upon our desire to add value for our shareholders and increasing our ability to meet the needs of cancer patients,” stated Rajesh C. Shrotriya, M.D., Chairman, President and Chief Executive Officer of Spectrum Pharmaceuticals, Inc. “Key to the acquisition is the diversification of our portfolio of marketed products by adding Allos’ FOLOTYN, which targets the same physicians as our ZEVALIN product.”

Dr. Shrotriya added, “We see a number of synergies between the two companies, which could result in significant savings. Our top priority continues to be to create an environment that nurtures talent and allows us to excel and enhance our presence in oncology markets where our products are making a difference. We are excited about the prospect of combining the two companies and in welcoming our new Allos colleagues to the Spectrum team.”

About Spectrum Pharmaceuticals, Inc.

Spectrum Pharmaceuticals is a leading biotechnology company focused on acquiring, developing, and commercializing drug products, with a primary focus in oncology and hematology. Spectrum currently markets two oncology drugs — FUSILEV^® (levoleucovorin) for Injection in the U.S. and ZEVALIN^® (ibritumomab tiuxetan) Injection for intravenous use, for which the Company has worldwide marketing rights. Spectrum’s strong track record in in-licensing and acquiring differentiated drugs, and expertise in clinical development have generated a robust, diversified, and growing pipeline of product candidates in advanced-stage Phase 2 and Phase 3 studies. More information on Spectrum is available at www.sppirx.com.

About Allos Therapeutics, Inc.

Allos Therapeutics is a biopharmaceutical company committed to the development and commercialization of innovative anti-cancer therapeutics. Allos is currently focused on the development and commercialization of FOLOTYN^® (pralatrexate injection), a folate analog metabolic inhibitor. FOLOTYN is approved in the U.S. for the treatment of patients with relapsed or refractory peripheral T-cell lymphoma (PTCL). This indication is based on overall response rate. Clinical benefit such as improvement in progression free survival or overall survival has not been demonstrated. Allos is also developing FOLOTYN in other hematologic malignancies and solid tumors. Allos is headquartered in Westminster, Colorado. For more information, please visit Allos’ website at www.allos.com.

About ZEVALIN^® and the ZEVALIN Therapeutic Regimen

ZEVALIN (ibritumomab tiuxetan) injection for intravenous use is indicated for the treatment of patients with relapsed or refractory, low-grade or follicular B-cell non-Hodgkin’s lymphoma (NHL). ZEVALIN is also indicated for the treatment of patients with previously untreated follicular non-Hodgkin’s Lymphoma who achieve a partial or complete response to first-line chemotherapy.

ZEVALIN is a CD20-directed radiotherapeutic antibody. The ZEVALIN therapeutic regimen consists of two components: rituximab, and Yttrium-90 (Y-90) radiolabeled ZEVALIN for therapy. ZEVALIN builds on the combined effect of a targeted biologic monoclonal antibody augmented with the therapeutic effects of a beta-emitting radioisotope.

Important ZEVALIN^® Safety Information

Deaths have occurred within 24 hours of rituximab infusion, an essential component of the ZEVALIN therapeutic regimen. These fatalities were associated with hypoxia, pulmonary infiltrates, acute respiratory distress syndrome, myocardial infarction, ventricular fibrillation, or cardiogenic shock. Most (80%) fatalities occurred with the first rituximab infusion. ZEVALIN administration can result in severe and prolonged cytopenias in most patients. Severe cutaneous and mucocutaneous reactions, some fatal, can occur with the ZEVALIN therapeutic regimen.

Please see full Prescribing Information, including BOXED WARNINGS, for ZEVALIN and rituximab. Full prescribing information for ZEVALIN can be found at www.ZEVALIN.com.

About FOLOTYN^®

FOLOTYN (pralatrexate injection), a folate analogue metabolic inhibitor, was discovered by Memorial Sloan-Kettering Cancer Center, SRI International and Southern Research Institute and developed by Allos Therapeutics. In September 2009, the U.S. Food and Drug Administration (FDA) granted accelerated approval for FOLOTYN for use as a single agent for the treatment of patients with relapsed or refractory PTCL. This indication is based on overall response rate. Clinical benefit such as improvement in progression-free survival or overall survival has not been demonstrated. FOLOTYN has been available to patients in the U.S. since October 2009. An updated analysis of data from PROPEL, the pivotal study of FOLOTYN in patients with relapsed or refractory PTCL, was published in the March 20, 2011 issue of the Journal of Clinical Oncology. FOLOTYN has patent protection through 2017 and potentially through July 2022, assuming a five-year patent term extension through the Hatch-Waxman Act. Please see full Prescribing Information for FOLOTYN at www.FOLOTYN.com.

Important FOLOTYN^® Safety Information

Warnings and Precautions

FOLOTYN may suppress bone marrow function, manifested by thrombocytopenia, neutropenia, and anemia. Monitor blood counts and omit or modify dose for hematologic toxicities.

Mucositis may occur. If greater-than or equal to Grade 2 mucositis is observed, omit or modify dose. Patients should be instructed to take folic acid and receive vitamin B12 to potentially reduce treatment-related hematological toxicity and mucositis.

Fatal dermatologic reactions may occur. Dermatologic reactions may be progressive and increase in severity with further treatment. Patients with dermatologic reactions should be monitored closely, and if severe, FOLOTYN should be withheld or discontinued. Tumor lysis syndrome may occur. Monitor patients and treat if needed.

FOLOTYN can cause fetal harm. Women should avoid becoming pregnant while being treated with FOLOTYN and pregnant women should be informed of the potential harm to the fetus.

Use caution and monitor patients when administering FOLOTYN to patients with moderate to severe renal function impairment.

Elevated liver function test abnormalities may occur and require monitoring. If liver function test abnormalities are greater-than or equal to Grade 3, omit or modify dose.

Adverse Reactions

The most common adverse reactions were mucositis (70%), thrombocytopenia (41%), nausea (40%), and fatigue (36%). The most common serious adverse events are pyrexia, mucositis, sepsis, febrile neutropenia, dehydration, dyspnea, and thrombocytopenia.

Use in Specific Patient Population

Nursing mothers should be advised to discontinue nursing or the drug, taking into consideration the importance of the drug to the mother.

Drug Interactions

Co-administration of drugs subject to renal clearance (e.g., probenecid, NSAIDs, and trimethoprim/sulfamethoxazole) may result in delayed renal clearance.

Please see FOLOTYN^® Full Prescribing Information at www.FOLOTYN.com.

Source: Spectrum Pharmaceuticals and Allos Therapeutics

This press release may contain forward-looking statements regarding future events of Spectrum Pharmaceuticals and Allos Therapeutics that involve risks and uncertainties that could cause actual results to differ materially. These statements are based on management’s current beliefs and expectations. Such forward-looking statements include statements relating to the ability of Spectrum Pharmaceuticals and Allos Therapeutics to complete the transactions contemplated by the Agreement and Plan of Merger dated as of April 4, 2012 (the “Merger Agreement”), including Spectrum Pharmaceuticals’ and Allos Therapeutics’ ability to satisfy the conditions to the consummation of the tender offer and the other conditions set forth in the Merger Agreement, the possibility of any termination of the Merger Agreement, and, if the transaction is completed, the success and strategic fit of the proposed combination of Spectrum Pharmaceuticals and Allos Therapeutics, the anticipated market and projected sales for FOLOTYN^® and the synergies for Spectrum Pharmaceuticals and Allos Therapeutics. The forward-looking statements contained in this document are subject to risks and uncertainties which may cause actual results to differ materially from

the forward-looking statements. Actual results may differ materially from current expectations because of risks associated with uncertainties as to the timing of the tender offer and the subsequent merger; uncertainties as to how many of Allos’ stockholders will tender their shares of common stock in the tender offer; the risk that competing offers or acquisition proposals will be made; the possibility that various conditions to the consummation of the offer or the merger may not be satisfied or waived, including that a governmental entity may prohibit, delay or refuse to grant approval for the consummation of the offer or the merger; the risk that stockholder litigation in connection with the tender offer or the merger may result in significant costs of defense, indemnification and liability; the possibility that the combined companies may not obtain synergies or perform as expected and the possibility that the anticipated market and projected sales for FOLOTYN^® may differ from those expected. Spectrum Pharmaceuticals and Allos Therapeutics do not plan to update any such forward-looking statements and expressly disclaim any duty to update the information contained in this press release except as required by law.

This press release is neither an offer to purchase nor a solicitation of an offer to sell securities. The tender offer is being made pursuant to a tender offer statement (including an offer to purchase, letter of transmittal, and related tender offer documents), which has been filed by Spectrum Pharmaceuticals and Sapphire Acquisition Sub, Inc. with the U.S. Securities and Exchange Commission (the “SEC”) on April 13, 2012, and has been subsequently amended. In addition, on April 13, 2012, Allos filed a solicitation/recommendation statement on Schedule 14D-9 with the SEC related to the tender offer, which has been subsequently amended. Stockholders of Allos are strongly advised to read the tender offer statement and the related solicitation/recommendation statement because they contain important information that stockholders should consider before making any decision regarding tendering their shares. The tender offer statement and certain other offer documents, as well as the solicitation/recommendation statement, will be made available to all Allos stockholders at no expense to them. These documents will be available at no charge on the SEC’s website at www.sec.gov. In addition, a copy of the tender offer statement will be made available free of charge to all stockholders of Allos who direct a request to MacKenzie Partners, Inc., the Information Agent for the offer, toll-free at (800) 322-2885.

Contacts:

Spectrum Pharmaceuticals

Shiv Kapoor

Vice President, Strategic Planning & Investor Relations

702-835-6300

Allos Therapeutics

Monique Greer

Vice President, Corporate Communications & Investor Relations

720-540-5268

Sources: Spectrum Pharmaceuticals and Allos Therapeutics