FORM OF DEBT SECURITIES WARRANT AGREEMENT

Exhibit 4.13

CELL THERAPEUTICS, INC.

and

[                                         ], as Warrant Agent

FORM OF DEBT SECURITIES

WARRANT AGREEMENT

Dated as of

[                                         ]

TABLE OF CONTENTS

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TABLE OF CONTENTS

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CELL THERAPEUTICS, INC.

Form of Debt Securities Warrant Agreement

DEBT SECURITIES WARRANT AGREEMENT , dated as of                                      between Cell Therapeutics, Inc., a Washington corporation (the “ Company ”) and                         , a [corporation] [national banking association] organized and existing under the laws of and having a corporate trust office in                     , as warrant agent (the “ Warrant Agent ”).

WHEREAS , the Company has entered into an indenture dated as of [                                     (the “ Senior Indenture ”), with                          , as trustee (such trustee, and any successors to such trustee, herein called the “ Senior Trustee ”), providing for the issuance from time to time of its unsubordinated debt securities, to be issued in one or more series as provided in the Senior Indenture (the “ Debt Securities ”);] [                         (the “ Subordinated Indenture ”), with                         , as trustee (such trustee, and any successors to such trustee, herein called the “ Subordinated Trustee ”), providing for the issuance from time to time of its subordinated debt securities, to be issued in one or more series as provided in the Subordinated Indenture (the “ Debt Securities ”);]

WHEREAS , the Company proposes to sell [If Warrants are sold with other securities—title of such other Securities being offered (the “ Other Securities ”) with] warrant certificates evidencing one or more warrants (the “ Warrants ” or, individually, a “ Warrant ”) representing the right to purchase [title of Debt Securities purchasable through exercise of Warrants] (the “ Warrant Debt Securities ”), such warrant certificates and other warrant certificates issued pursuant to this Agreement being herein called the “ Warrant Certificates ”; and

WHEREAS , the Company desires the Warrant Agent to act on behalf of the Company, and the Warrant Agent is willing so to act, in connection with the issuance, registration, transfer, exchange, exercise and replacement of the Warrant Certificates, and in this Agreement wishes to set forth, among other things, the form and provisions of the Warrant Certificates and the terms and conditions on which they may be issued, registered, transferred, exchanged, exercised and replaced;

NOW, THEREFORE , in consideration of the premises and of the mutual agreements herein contained, the parties hereto agree as follows:

ARTICLE 1

ISSUANCE OF WARRANTS AND EXECUTION AND

DELIVERY OF WARRANT CERTIFICATES

1.1 Issuance of Warrants. [If Warrants alone—Upon issuance, each Warrant Certificate shall evidence one or more Warrants.] [If Other Securities and Warrants—Warrant Certificates shall be [initially] issued in connection with the issuance of the Other Securities [but shall be separately transferable on and after                          (the “ Detachable Date ”)] [and shall not be separately transferable] and each Warrant Certificate shall evidence one or more Warrants.] Each Warrant evidenced thereby shall represent the right, subject to the provisions contained herein and therein, to purchase one Warrant Debt Security. [If Other Securities and Warrants—

Warrant Certificates shall be initially issued in units with the Other Securities and each Warrant Certificate included in such a unit shall evidence                          Warrants for each [$             principal amount] [                         shares] of Other Securities included in such unit.].

1.2 Execution and Delivery of Warrant Certificates. Each Warrant Certificate, whenever issued, shall be in registered form substantially in the form set forth in Exhibit A hereto, shall be dated the date of its countersignature by the Warrant Agent and may have such letters, numbers, or other marks of identification or designation and such legends or endorsements printed, lithographed or engraved thereon as the officers of the Company executing the same may approve (execution thereof to be conclusive evidence of such approval) and as are not inconsistent with the provisions of this Agreement, or as may be required to comply with any law or with any rule or regulation made pursuant thereto or with any rule or regulation of any securities exchange on which the Warrants may be listed, or to conform to usage. The Warrant Certificates shall be signed on behalf of the Company by any of its present or future chief executive officers, presidents, executive vice presidents, vice presidents, chief financial officers, chief legal officers, treasurers, assistant treasurers, controllers, assistant controllers, secretaries or assistant secretaries under its corporate seal reproduced thereon. Such signatures may be manual or facsimile signatures of such authorized officers and may be imprinted or otherwise reproduced on the Warrant Certificates. The seal of the Company may be in the form of a facsimile thereof and may be impressed, affixed, imprinted or otherwise reproduced on the Warrant Certificates.

No Warrant Certificate shall be valid for any purpose, and no Warrant evidenced thereby shall be exercisable, until such Warrant Certificate has been countersigned by the manual signature of the Warrant Agent. Such signature by the Warrant Agent upon any Warrant Certificate executed by the Company shall be conclusive evidence that the Warrant Certificate so countersigned has been duly issued hereunder.

In case any officer of the Company who shall have signed any of the Warrant Certificates either manually or by facsimile signature shall cease to be such officer before the Warrant Certificates so signed shall have been countersigned and delivered by the Warrant Agent, such Warrant Certificates may be countersigned and delivered notwithstanding that the person who signed Warrant Certificates ceased to be such officer of the Company; and any Warrant Certificate may be signed on behalf of the Company by such persons as, at the actual date of the execution of such Warrant Certificate, shall be the proper officers of the Company, although at the date of the execution of this Agreement any such person was not such officer.

The term “holder” or “holder of a Warrant Certificate” as used herein shall mean any person in whose name at the time any Warrant Certificate shall be registered upon the books to be maintained by the Warrant Agent for that purpose [If Other Securities and Warrants are not immediately detachable—or upon the registration of the Other Securities prior to the Detachable Date. Prior to the Detachable Date, the Company will, or will cause the registrar of the Other Securities to, make available at all times to the Warrant Agent such information as to holders of the Other Securities as may be necessary to keep the Warrant Agent’s records up to date].

1.3 Issuance of Warrant Certificates. Warrant Certificates evidencing the right to purchase Warrant Debt Securities may be executed by the Company and delivered to the

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Warrant Agent upon the execution of this Warrant Agreement or from time to time thereafter. The Warrant Agent shall, upon receipt of Warrant Certificates duly executed on behalf of the Company, countersign such Warrant Certificates and shall deliver such Warrant Certificates to or upon the order of the Company.

ARTICLE 2

WARRANT PRICE, DURATION AND EXERCISE OF WARRANTS

2.1 Warrant Price. During the period specified in Section 2.2, each Warrant shall, subject to the terms of this Warrant Agreement and the applicable Warrant Certificate, entitle the holder thereof, to purchase the principal amount of Warrant Debt Securities specified in the applicable Warrant Certificate at an exercise price of             % of the principal amount thereof [plus accrued amortization, if any, of the original issue discount of the Warrant Debt Securities] [plus accrued interest, if any, from the most recent date from which interest shall have been paid on the Warrant Debt Securities or, if no interest shall have been paid on the Warrant Debt Securities, from the date of their initial issuance.] [The original issue discount ($             for each $1,000 principal amount of Warrant Debt Securities) will be amortized at a             % annual rate, computed on a[n] [semi-] annual basis [using a 360-day year consisting of twelve 30-day months].] Such purchase price for the Warrant Debt Securities is referred to in this Agreement as the “ Warrant Price .”

2.2 Duration of Warrants. Each Warrant may be exercised in whole or in part at any time, as specified herein, on or after [the date thereof] [            ] and at or before [            ] p.m., [City] time, on              or such later date as the Company may designate by notice to the Warrant Agent and the holders of Warrant Certificates mailed to their addresses as set forth in the record books of the Warrant Agent (the “Expiration Date”). Each Warrant not exercised at or before [            ] p.m., [City] time, on the Expiration Date shall become void, and all rights of the holder of the Warrant Certificate evidencing such Warrant under this Agreement shall cease.

2.3 Exercise of Warrants.

(a) During the period specified in Section 2.2, the Warrants may be exercised to purchase a whole number of Warrant Debt Securities in registered form by providing certain information as set forth on the reverse side of the Warrant Certificate and by paying in full, in lawful money of the United States of America, [in cash or by certified check or official bank check in New York Clearing House funds] [by bank wire transfer in immediately available funds] the Warrant Price for each Warrant Debt Security with respect to which a Warrant is being exercised to the Warrant Agent at its corporate trust office, provided that such exercise is subject to receipt within five business days of such payment by the Warrant Agent of the Warrant Certificate with the form of election to purchase Warrant Debt Securities set forth on the reverse side of the Warrant Certificate properly completed and duly executed. The date on which payment in full of the Warrant Price is received by the Warrant Agent shall, subject to receipt of the Warrant Certificate as aforesaid, be deemed to be the date on which the Warrant is exercised; provided, however, that if, at the date of receipt of such Warrant Certificates and payment in full

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of the Warrant Price, the transfer books for the Warrant Debt Securities purchasable upon the exercise of such Warrants shall be closed, no such receipt of such Warrant Certificates and no such payment of such Warrant Price shall be effective to constitute the person so designated to be named as the holder of record of such Warrant Debt Securities on such date, but shall be effective to constitute such person as the holder of record of such Warrant Debt Securities for all purposes at the opening of business on the next succeeding day on which the transfer books for the Warrant Debt Securities purchasable upon the exercise of such Warrants shall be opened, and the certificates for the Warrant Debt Securities in respect of which such Warrants are then exercised shall be issuable as of the date on such next succeeding day on which the transfer books shall next be opened, and until such date the Company shall be under no duty to deliver any certificate for such Warrant Debt Securities. The Warrant Agent shall deposit all funds received by it in payment of the Warrant Price in an account of the Company maintained with it and shall advise the Company by telephone at the end of each day on which a payment for the exercise of Warrants is received of the amount so deposited to its account. The Warrant Agent shall promptly confirm such telephone advice to the Company in writing.

(b) The Warrant Agent shall, from time to time, as promptly as practicable, advise the Company of (i) the number of Warrant Debt Securities with respect to which Warrants were exercised, (ii) the instructions of each holder of the Warrant Certificates evidencing such Warrants with respect to delivery of the Warrant Debt Securities to which such holder is entitled upon such exercise, (iii) delivery of Warrant Certificates evidencing the balance, if any, of the Warrants for the remaining Warrant Debt Securities after such exercise, and (iv) such other information as the Company or the [Senior] [Subordinated] Trustee shall reasonably require.

(c) As soon as practicable after the exercise of any Warrant, the Company shall issue, pursuant to the Indenture, in authorized denominations, to or upon the order of the holder of the Warrant Certificate evidencing such Warrant, the Warrant Debt Securities to which such holder is entitled, in fully registered form, registered in such name or names as may be directed by such holder. If fewer than all of the Warrants evidenced by such Warrant Certificate were exercised, the Company shall execute, and an authorized officer of the Warrant Agent shall manually countersign and deliver, a new Warrant Certificate evidencing Warrants for the number of Warrant Debt Securities remaining unexercised.

(d) The Company shall not be required to pay any stamp or other tax or other governmental charge required to be paid in connection with any transfer involved in the issue of the Warrant Debt Securities, and in the event that any such transfer is involved, the Company shall not be required to issue or deliver any Warrant Debt Securities until such tax or other charge shall have been paid or it has been established to the Company’s satisfaction that no such tax or other charge is due.

ARTICLE 3

OTHER PROVISIONS RELATING TO RIGHTS OF

HOLDERS OF WARRANT CERTIFICATES

3.1 No Rights as Holders of Warrant Debt Securities Conferred by Warrants or Warrant Certificates. No Warrant Certificate or Warrant evidenced thereby shall

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entitle the holder thereof to any of the rights of a holder of Warrant Debt Securities, including, without limitation, the right to receive the payment of principal of (or premium, if any) or interest, if any, on the Warrant Debt Securities or to enforce any of the covenants in the Indenture.

3.2 Lost, Stolen, Mutilated or Destroyed Warrant Certificates. Upon receipt by the Warrant Agent of evidence reasonably satisfactory to it and the Company of the ownership of and the loss, theft, destruction or mutilation of any Warrant Certificate and/or indemnity reasonably satisfactory to the Warrant Agent and the Company and, in the case of mutilation, upon surrender of the mutilated Warrant Certificate to the Warrant Agent for cancellation, then, in the absence of notice to the Company or the Warrant Agent that such Warrant Certificate has been acquired by a bona fide purchaser, the Company shall execute, and an authorized officer of the Warrant Agent shall manually countersign and deliver, in exchange for or in lieu of the lost, stolen, destroyed or mutilated Warrant Certificate, a new Warrant Certificate of the same tenor and evidencing Warrants for a like principal amount of Warrant Debt Securities. Upon the issuance of any new Warrant Certificate under this Section 3.2, the Company may require the payment of a sum sufficient to cover any tax or other governmental charge that may be imposed in relation thereto and any other expenses (including the fees and expenses of the Warrant Agent) in connection therewith. Every substitute Warrant Certificate executed and delivered pursuant to this Section 3.2 in lieu of any lost, stolen or destroyed Warrant Certificate shall represent an additional contractual obligation of the Company, whether or not the lost, stolen or destroyed Warrant Certificate shall be at any time enforceable by anyone, and shall be entitled to the benefits of this Agreement equally and proportionately with any and all other Warrant Certificates duly executed and delivered hereunder. The provisions of this Section 3.2 are exclusive and shall preclude (to the extent lawful) all other rights and remedies with respect to the replacement of mutilated, lost, stolen or destroyed Warrant Certificates.

3.3 Holder of Warrant Certificate May Enforce Rights. Notwithstanding any of the provisions of this Agreement, any holder of any Warrant Certificate, without the consent of the Warrant Agent, the [Senior] [Subordinated] Trustee, the holder of any Warrant Debt Securities or the holder of any other Warrant Certificate, may, in such holder’s own behalf and for such holder’s own benefit, enforce, and may institute and maintain any suit, action or proceeding against the Company suitable to enforce, or otherwise in respect of, such holder’s right to exercise the Warrants evidenced by such holder’s Warrant Certificate in the manner provided in such holder’s Warrant Certificates and in this Agreement.

3.4 Merger, Sale, Conveyance or Lease. In case of (a) any share exchange, merger or similar transaction of the Company with or into another person or entity (other than a share exchange, merger or similar transaction in which the Company is the acquiring or surviving corporation) or (b) the sale, exchange, lease, transfer or other disposition of all or substantially all of the properties and assets of the Company as an entirety (in any such case, a “ Reorganization Event ”), then, as a condition of such Reorganization Event, lawful provisions shall be made, and duly executed documents evidencing the same from the Company’s successor shall be delivered to the holders of the Warrants, so that such successor shall succeed to and be substituted for the Company, and assume all the Company’s obligations under, this Agreement and the Warrants. The Company shall thereupon be relieved of any further obligation hereunder

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or under the Warrants, and the Company as the predecessor corporation may thereupon or at any time thereafter be dissolved, wound up or liquidated. Such successor or assuming entity thereupon may cause to be signed, and may issue either in its own name or in the name of the Company, any or all of the Warrants issuable hereunder which heretofore shall not have been signed by the Company, and may execute and deliver securities in its own name, in fulfillment of its obligations to deliver Warrant Debt Securities upon exercise of the Warrants. All the Warrants so issued shall in all respects have the same legal rank and benefit under this Agreement as the Warrants theretofore or thereafter issued in accordance with the terms of this Agreement as though all of such Warrants had been issued at the date of the execution hereof. In any case of any such Reorganization Event, such changes in phraseology and form (but not in substance) may be made in the Warrants thereafter to be issued as may be appropriate.

The Warrant Agent may receive a written opinion of legal counsel as conclusive evidence that any such Reorganization Event complies with the provisions of this Section 3.4.

3.5 Notice to Warrantholders. In case the Company shall (a) effect any Reorganization Event or (b) make any distribution on or in respect of the [title of Warrant Debt Securities] in connection with the dissolution, liquidation or winding up of the Company, then the Company shall mail to each holder of Warrants at such holder’s address as it shall appear on the books of the Warrant Agent, at least ten days prior to the applicable date hereinafter specified, a notice stating the date on which such Reorganization Event, dissolution, liquidation or winding up is expected to become effective, and the date as of which it is expected that holders of [title of Warrant Debt Securities] of record shall be entitled to exchange their shares of [title of Warrant Debt Securities] for securities or other property deliverable upon such Reorganization Event, dissolution, liquidation or winding up. No failure to mail such notice nor any defect therein or in the mailing thereof shall affect any such transaction.

ARTICLE 4

EXCHANGE AND TRANSFER OF WARRANT CERTIFICATES

4.1 Exchange and Transfer of Warrant Certificates. [If Other Securities with Warrants which are immed