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                                                                    Exhibit 10.1

                                                               EXECUTION VERSION

                           Enzon Pharmaceuticals, Inc.

                      4% Convertible Senior Notes due 2013


                          REGISTRATION RIGHTS AGREEMENT

                                                                    May 23, 2006
Goldman, Sachs & Co.,
As representative of the several Purchasers
   named in Schedule I to the Purchase Agreement
85 Broad Street
New York, New York 10004

Ladies and Gentlemen:

         Enzon Pharmaceuticals, Inc., a Deleware corporation (the "Company"),
proposes to issue and sell to the Purchasers (as defined herein) upon the terms
set forth in the Purchase Agreement (as defined herein) up to $275 million
aggregate principal amount of its 4% Convertible Senior Notes due 2013 (the
"Securities"). As an inducement to the Purchasers to enter into the Purchase
Agreement and in satisfaction of a condition to the obligations of the
Purchasers thereunder, the Company agrees with the Purchasers for the benefit of
Holders (as defined herein) from time to time of the Registrable Securities (as
defined herein) as follows:

         1. Definitions.

         (a) Capitalized terms used herein without definition shall have the
meanings ascribed to them in the Purchase Agreement. As used in this Agreement,
the following defined terms shall have the following meanings:

         "Additional Interest" has the meaning assigned thereto in Section 7(a)
hereof.

         "Affiliate" of any specified person means any other person which,
directly or indirectly, is in control of, is controlled by, or is under common
control with such specified person. For purposes of this definition, control of
a person means the power, direct or indirect, to direct or cause the direction
of the management and policies of such person whether by contract or otherwise;
and the terms "controlling" and "controlled" have meanings correlative to the
foregoing.

         "Closing Date" means the First Time of Delivery as defined in the
Purchase Agreement.

         "Commission" means the United States Securities and Exchange
Commission, or any other federal agency at the time administering the Exchange
Act or the Securities Act, whichever is the relevant statute for the particular
purpose.

         "Common Stock" means the Company's common stock, par value $0.01 per
share, together with any associated preferred share purchase rights.


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         "DTC" means The Depository Trust Company.

         "Effective Date" has the meaning assigned thereto in Section 2(b)(i)
hereof.

         "Effective Failure" has the meaning assigned thereto in Section 7(b)
hereof.

         "Effectiveness Period" has the meaning assigned thereto in Section
2(b)(i) hereof.

         "Effective Time" means the time at which the Commission declares the
Shelf Registration Statement effective or at which the Shelf Registration
Statement otherwise becomes effective.

         "Electing Holder" has the meaning assigned thereto in Section 3(a)(iii)
hereof.

         "Exchange Act" means the United States Securities Exchange Act of 1934,
as amended.

         "Holder" means any person that is the record owner of Registrable
Securities (and includes any person that has a beneficial interest in any
Registrable Security in book-entry form).

         "Indenture" means the Indenture, dated as of May 23, 2006, between the
Company and Wilmington Trust Company, as amended and supplemented from time to
time in accordance with its terms.

         "Managing Underwriters" means the investment banker or investment
bankers and manager or managers that shall administer an underwritten offering,
if any, conducted pursuant to Section 6 hereof.

         "NASD Rules" means the Rules of the National Association of Securities
Dealers, Inc., as amended from time to time.

         "Notice and Questionnaire" means a Notice of Registration Statement and
Selling Securityholder Questionnaire substantially in the form of Appendix A
hereto.

         The term "person" means an individual, partnership, corporation, trust
or unincorporated organization, or a government or agency or political
subdivision thereof.

         "Prospectus" means the prospectus (including, without limitation, any
preliminary prospectus, any final prospectus and any prospectus that discloses
information previously omitted from a prospectus filed as part of an effective
registration statement in reliance upon Rule 430A under the Securities Act)
included in the Shelf Registration Statement, as amended or supplemented by any
prospectus supplement with respect to the terms of the offering of any portion
of the Registrable Securities covered by the Shelf Registration Statement and by
all other amendments and supplements to such prospectus, including all material
incorporated by reference in such prospectus and all documents filed after the
date of such prospectus by the Company under the Exchange Act and incorporated
by reference therein.


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         "Purchase Agreement" means the purchase agreement, dated as of May 17,
2006, between the Purchasers and the Company relating to the Securities.

         "Purchasers" means the Purchasers named in Schedule I to the Purchase
Agreement.

         "Registrable Securities" means all or any portion of the Securities
issued on the date hereof (or pursuant to the Purchasers' over-allotment option
as described in the Purchase Agreement) under the Indenture in registered form
and the shares of Common Stock issuable upon conversion of such Securities;
provided, however, that a security ceases to be a Registrable Security when it
is no longer a Restricted Security.

         "Registration Default" has the meaning assigned thereto in Section 7(a)
hereof.

         "Restricted Security" means any Security or share of Common Stock
issuable upon conversion thereof except any such Security or share of Common
Stock that (i) has been effectively registered under the Securities Act and sold
in a manner contemplated by the Shelf Registration Statement, (ii) has been
transferred in compliance with Rule 144 under the Securities Act (or any
successor provision thereto) or is transferable pursuant to paragraph (k) of
such Rule 144 (or any successor provision thereto) or (iii) has otherwise been
transferred and a new Security or share of Common Stock not subject to transfer
restrictions under the Securities Act has been delivered by or on behalf of the
Company in accordance with Section 2.1 of the Indenture.

         "Rules and Regulations" means the published rules and regulations of
the Commission promulgated under the Securities Act or the Exchange Act, as
applicable, as in effect at any relevant time.

         "Securities Act" means the United States Securities Act of 1933, as
amended.

         "Shelf Registration" means a registration effected pursuant to Section
2 hereof.

         "Shelf Registration Statement" means a "shelf" registration statement
filed under the Securities Act providing for the registration of, and the sale
on a continuous or delayed basis by the Holders of, all of the Registrable
Securities pursuant to Rule 415 under the Securities Act and/or any similar rule
that may be adopted by the Commission, filed by the Company pursuant to the
provisions of Section 2 of this Agreement, including the Prospectus contained
therein, any amendments and supplements to such registration statement,
including post-effective amendments, and all exhibits and all material
incorporated by reference in such registration statement.

         "Trust Indenture Act" means the Trust Indenture Act of 1939, or any
successor thereto, and the rules, regulations and forms promulgated thereunder,
as the same shall be amended from time to time.

         The term "underwriter" means any underwriter of Registrable Securities
in connection with an offering thereof under a Shelf Registration Statement.


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         (b) Wherever there is a reference in this Agreement to a percentage of
the "principal amount" of Registrable Securities or to a percentage of
Registrable Securities, Common Stock constituting Registrable Securities shall
be treated as representing the principal amount of Securities that was
surrendered for conversion or exchange in order to receive such number of shares
of Common Stock.

         2. Shelf Registration.

         (a) The Company shall file with the Commission, no later than 90
calendar days following the Closing Date, if at such time the Company is
eligible to file a registration statement on Form S-3 or, if the company is not
eligible to file a Shelf Registration Statement on Form S-3, no later than 135
calendar days after the Closing Date, a Shelf Registration Statement relating to
the offer and sale of the Registrable Securities by the Holders from time to
time in accordance with the methods of distribution elected by such Holders and
set forth in such Shelf Registration Statement and, thereafter, if the Company
is required to file a Shelf Registration Statement covering resales of the
Registrable Securities no later than 90 calendar days after the Closing Date,
shall use its reasonable best efforts to cause such Shelf Registration Statement
to be declared effective under the Securities Act no later than 180 calendar
days following the Closing Date or, if the Company is required to file such
Shelf Registration Statement no later than 135 calendar days after the Closing
Date, use its reasonable best efforts to cause the Shelf Registration Statement
to be declared effective under the Securities Act no later than 225 days after
the Closing Date; provided, however, that the Company may, upon written notice
to all Holders, postpone having the Shelf Registration Statement declared
effective for a reasonable period not to exceed 90 days if the Company possesses
material non-public information, the disclosure of which would have a material
adverse effect on the Company and its subsidiaries taken as a whole; provided,
further, however, that no Holder shall be entitled to be named as a selling
securityholder in the Shelf Registration Statement or to use the Prospectus
forming a part thereof for resales of Registrable Securities unless such Holder
is an Electing Holder.

         (b) The Company shall use its reasonable best efforts:

             (i) to keep the Shelf Registration Statement continuously
         effective under the Securities Act in order to permit the Prospectus
         forming a part thereof to be usable by Holders until the earliest of
         (1) the sale of all Registrable Securities registered under the Shelf
         Registration Statement; (2) the expiration of the period referred to in
         Rule 144(k) of the Securities with respect to all Registrable
         Securities held by Persons that are not Affiliates of the Company; and
         (3) two years from the date (the "Effective Date") such Shelf
         Registration Statement is declared effective (such period being
         referred to herein as the "Effectiveness Period");

             (ii) after the Effective Time of the Shelf Registration Statement,
         promptly upon the request of any Holder of Registrable Securities that
         is not then an Electing Holder, to take any action reasonably necessary
         to enable such Holder to use the Prospectus forming a part thereof for
         resales of Registrable Securities, including, without limitation, any
         action necessary to identify such Holder as a selling securityholder in
         the Shelf Registration Statement; provided, however, that nothing in
         this subparagraph shall relieve such Holder of the obligation to return
         a completed and signed Notice and Questionnaire to the Company in
         accordance with Section 3(a)(ii) hereof; and


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             (iii) if at any time the Securities, pursuant to Section 4.2 of
         the Indenture, are convertible into securities other than Common Stock,
         to cause, or to cause any successor under the Indenture to cause, such
         securities to be included in the Shelf Registration Statement no later
         than the date on which the Securities may then be convertible into such
         securities.

The Company shall be deemed not to have used its reasonable best efforts to keep
the Shelf Registration Statement effective during the requisite period if the
Company voluntarily takes any action that would result in Holders of Registrable
Securities covered thereby not being able to offer and sell any of such
Registrable Securities during that period, unless such action is (A) required by
applicable law and the Company thereafter promptly complies with the
requirements of paragraph 3(j) below or (B) permitted pursuant to Section 2(c)
below.

         (c) The Company may suspend the use of the Prospectus for a period
not to exceed 30 days in any 90-day period or an aggregate of 90 days in any
12-month period if the Board of Directors of the Company shall have determined
in good faith that because of valid business reasons (not including avoidance of
the Company's obligations hereunder), including the acquisition or divestiture
of assets, pending corporate developments and similar events, it is in the best
interests of the Company to suspend such use, and prior to suspending such use
the Company provides the Holders with written notice of such suspension, which
notice need not specify the nature of the event giving rise to such suspension.

         3. Registration Procedures. In connection with the Shelf Registration
Statement, the following provisions shall apply:

         (a) (i) Not less than 30 calendar days prior to the Effective Time of
the Shelf Registration Statement, the Company shall mail the Notice and
Questionnaire to the Holders of Registrable Securities or provide the Notice and
Questionnaire to DTC, as applicable. No Holder shall be entitled to be named as
a selling securityholder in the Shelf Registration Statement as of the Effective
Time, and no Holder shall be entitled to use the Prospectus forming a part
thereof for resales of Registrable Securities at any time, unless such Holder
has returned a completed and signed Notice and Questionnaire to the Company by
the deadline for response set forth therein; provided, however, Holders of
Registrable Securities shall have at least 28 calendar days from the date on
which the Notice and Questionnaire is first mailed to such Holders to return a
completed and signed Notice and Questionnaire to the Company.

             (ii) After the Effective Time of the Shelf Registration Statement,
         the Company shall, upon the request of any Holder of Registrable
         Securities that is not then an Electing Holder, promptly send a Notice
         and Questionnaire to such Holder. The Company shall not be required to
         take any action to name such Holder as a selling securityholder in the
         Shelf Registration Statement or to enable such Holder to use the
         Prospectus forming a part thereof for resales of Registrable Securities
         until such Holder has returned a completed and signed Notice and
         Questionnaire to the Company.


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             (iii) The term "Electing Holder" shall mean any Holder of
         Registrable Securities that has returned a completed and signed Notice
         and Questionnaire to the Company in accordance with Section 3(a)(i) or
         3(a)(ii) hereof.

         (b) Upon the Electing Holders' request, the Company shall furnish to
each Electing Holder, prior to the Effective Time, a copy of the Shelf
Registration Statement initially filed with the Commission, and shall furnish to
such Holders, prior to the filing thereof with the Commission, copies of each
amendment thereto and each amendment or supplement, if any, to the Prospectus
included therein, and shall use all reasonable efforts to reflect in each such
document, at the Effective Time or when so filed with the Commission, as the
case may be, such comments as such Holders and their respective counsel
reasonably may propose.

         (c) The Company shall promptly take such action as may be necessary so
that (i) each of the Shelf Registration Statement and any amendment thereto and
the Prospectus forming a part thereof and any amendment or supplement thereto
(and each report or other document incorporated therein by reference in each
case) complies in all material respects with the Securities Act and the Exchange
Act and the respective rules and regulations thereunder, (ii) each of the Shelf
Registration Statement and any amendment thereto does not, when it becomes
effective, contain an untrue statement of a material fact or omit to state a
material fact required to be stated therein or necessary to make the statements
therein not misleading and (iii) each of the Prospectus forming a part of the
Shelf Registration Statement, and any amendment or supplement to such
Prospectus, does not at any time during the Effectiveness Period include an
untrue statement of a material fact or omit to state a material fact necessary
in order to make the statements therein, in the light of the circumstances under
which they were made, not misleading.

         (d) The Company shall promptly advise each Electing Holder, and shall
confirm such advice in writing if so requested by any such Electing Holder:

             (i) when a Shelf Registration Statement or any post-effective
         amendment thereto has become effective, in each case making a public
         announcement thereof by release made to Reuters Economic Services and
         Bloomberg Business News;

             (ii) of the issuance by the Commission of any stop order suspending
         the effectiveness of the Shelf Registration Statement or the initiation
         of any proceedings for such purpose;

             (iii) of the receipt by the Company of any notification with
         respect to the suspension of the qualification of the securities
         included in the Shelf Registration Statement for sale in any
         jurisdiction or the initiation of any proceeding for such purpose; and

             (iv) of the occurrence of any event or the existence of any state
         of facts that requires the making of any changes in the Shelf
         Registration Statement or the Prospectus included therein so that, as
         of such date, such Shelf Registration Statement and Prospectus do not
         contain an untrue statement of a material fact and do not omit to state
         a material fact required to be stated therein or necessary to make the
         statements therein (in the case of the Prospectus, in light of the
         circumstances under which they were made) not misleading (which advice
         shall be accompanied by an instruction to such Holders to suspend the
         use of the Prospectus until the requisite changes have been made).


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         (e) The Company shall use all reasonable efforts to prevent the
issuance, and if issued to obtain the withdrawal at the earliest possible time,
of any order suspending the effectiveness of the Shelf Registration Statement.

         (f) If such Electing Holder so requests in writing, the Company shall
furnish to each Electing Holder, without charge, at least one copy of the Shelf
Registration Statement and all post-effective amendments thereto, including
financial statements and schedules, and, all reports, other documents and
exhibits that are filed with or incorporated by reference in the Shelf
Registration Statement.

         (g) The Company shall, during the Effectiveness Period, deliver to each
Electing Holder, without charge, as many copies of the Prospectus (including
each preliminary Prospectus) included in the Shelf Registration Statement and
any amendment or supplement thereto as such Electing Holder may reasonably
request; and the Company consents (except during the periods specified in
Section 2(c) above or during the continuance of any event or the existence of
any state of facts described in Sections 3(d)(iii) and (iv) above) to the use of
the Prospectus and any amendment or supplement thereto by each of the Electing
Holders in connection with the offering and sale of the Registrable Securities
covered by the Prospectus and any amendment or supplement thereto during the
Effectiveness Period.

         (h) Prior to any offering of Registrable Securities pursuant to the
Shelf Registration Statement, the Company shall use all reasonable efforts to
(i) register or qualify or cooperate with the Electing Holders and their
respective counsel in connection with the registration or qualification of such
Registrable Securities for offer and sale under the securities or "blue sky"
laws of such jurisdictions within the United States as any Electing Holder may
reasonably request, (ii) keep such registrations or qualifications in effect and
comply with such laws so as to permit the continuance of offers and sales in
such jurisdictions for so long as may be necessary to enable any Electing Holder
or underwriter, if any, to complete its distribution of Registrable Securities
pursuant to the Shelf Registration Statement, and (iii) take any and all other
actions necessary or advisable to enable the disposition in such jurisdictions
of such Registrable Securities; provided, however, that in no event shall the
Company be obligated to (A) qualify as a foreign corporation or as a dealer in
securities in any jurisdiction where it would not otherwise be required to so
qualify but for this Section 3(h) or (B) file any general consent to service of
process in any jurisdiction where it is not as of the date hereof so subject.

         (i) Unless any Registrable Securities shall be in book-entry only form,
the Company shall cooperate with the Electing Holders to facilitate the timely
preparation and delivery of certificates representing Registrable Securities to
be sold pursuant to the Shelf Registration Statement, which certificates, if so
required by any securities exchange upon which any Registrable Securities are
listed, shall be penned, lithographed or engraved, or produced by any
combination of such methods, on steel engraved borders, and which certificates
shall be free of any restrictive legends and in such permitted denominations and
registered in such names as Electing Holders may request in connection with the
sale of Registrable Securities pursuant to the Shelf Registration Statement.


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         (j) Upon the occurrence of any event or the existence of any state of
facts contemplated by paragraph 3(d)(iv) above, the Company shall promptly
prepare a post-effective amendment to any Shelf Registration Statement or an
amendment or supplement to the related Prospectus or file any other required
document so that, as thereafter delivered to purchasers of the Registrable
Securities included therein, the Prospectus will not include an untrue statement
of a material fact or omit to state any material fact necessary to make the
statements therein, in the light of the circumstances under which they were
made, not misleading. If the Company notifies the Electing Holders of the
occurrence of any event or the existence of any state of facts contemplated by
paragraph 3(d)(iv) above, the Electing Holder shall suspend the use of the
Prospectus until the requisite changes to the Prospectus have been made.

         (k) Not later than the Effective Time of the Shelf Registration
Statement, the Company shall provide a CUSIP number for the Registrable
Securities that are debt securities.

         (l) The Company shall use all reasonable efforts to comply with all
applicable Rules and Regulations, and to make generally available to its
securityholders as soon as practicable, but in any event not later than eighteen
months after (i) the effective date (as defined in Rule 158(c) under the
Securities Act) of the Shelf Registration Statement, (ii) the effective date of
each post-effective amendment to the Shelf Registration Statement, and (iii) the
date of each filing by the Company with the Commission of an Annual Report on
Form 10-K that is incorporated by reference in the Shelf Registration Statement,
an earnings statement of the Company and its subsidiaries complying with Section
11(a) of the Securities Act and the rules and regulations of the Commission
thereunder (including, at the option of the Company, Rule 158).

         (m) Not later than the Effective Time of the Shelf Registration
Statement, the Company shall cause the Indenture to be qualified under the Trust
Indenture Act; in connection with such qualification, the Company shall
cooperate with the Trustee under the Indenture and the Holders (as defined in
the Indenture) to effect such changes to the Indenture as may be required for
such Indenture to be so qualified in accordance with the terms of the Trust
Indenture Act; and the Company shall execute, and shall use all reasonable
efforts to cause the Trustee to execute, all documents that may be required to
effect such changes and all other forms and documents required to be filed with
the Commission to enable such Indenture to be so qualified in a timely manner.
In the event that any such amendment or modification referred to in this Section
3(m) involves the appointment of a new trustee under the Indenture, the Company
shall appoint a new trustee thereunder pursuant to the applicable provisions of
the Indenture.

         (n) In the event of an underwritten offering conducted pursuant to
Section 6 hereof, the Company shall, if requested, promptly include or
incorporate in a Prospectus supplement or post-effective amendment to the Shelf
Registration Statement such information as the Managing Underwriters reasonably
agree should be included therein and to which the Company does not reasonably
object and shall make all required filings of such Prospectus supplement or
post-effective amendment as soon as practicable after it is notified of the
matters to be included or incorporated in such Prospectus supplement or
post-effective amendment.


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         (o) The Company shall enter into such customary agreements (including
an underwriting agreement in customary form in the event of an underwritten
offering conducted pursuant to Section 6 hereof) and take all other appropriate
action in order to expedite and facilitate the registration and disposition of
the Registrable Securities, and in connection therewith, if an underwriting
agreement is entered into, cause the same to contain indemnification provisions
and procedures substantially identical to those set forth in Section 5 hereof
with respect to all parties to be indemnified pursuant to Section 5 hereof.

         (p) The Company shall:

             (i)(A) make reasonably available for inspection by the Electing
         Holders, any underwriter participating in any disposition pursuant to
         the Shelf Registration Statement, and any attorney, accountant or other
         agent retained by such Electing Holders or any such underwriter all
         relevant financial and other records, pertinent corporate documents and
         properties of the Company and its subsidiaries, and (B) cause the
         Company's officers, directors and employees to supply all information
         reasonably requested by such Electing Holders or any such underwriter,
         attorney, accountant or agent in connection with the Shelf Registration
         Statement, in each case, as is customary for similar due diligence
         examinations; provided, however, that all records, information and
         documents that are designated in writing by the Company, in good faith,
         as confidential shall be kept confidential by such Electing Holders and
         any such underwriter, attorney, accountant or agent, unless such
         disclosure is made in connection with a court proceeding or required by
         law, or such records, information or documents become available to the
         public generally or through a third party without an accompanying
         obligation of confidentiality; and provided further that, if the
         foregoing inspection and information gathering would otherwise disrupt
         the Company's conduct of its business, such inspection and information
         gathering shall, to the greatest extent possible, be coordinated on
         behalf of the Electing Holders and the other parties entitled thereto
         by one counsel designated by and on behalf of the Electing Holders and
         other parties;

             (ii) in connection with any underwritten offering conducted
         pursuant to Section 6 hereof, make such representations and warranties
         to the Electing Holders participating in such underwritten offering and
         to the Managing Underwriters, in form, substance and scope as are
         customarily made by the Company to underwriters in primary underwritten
         offerings of equity and convertible debt securities and covering
         matters including, but not limited to, those set forth in the Purchase
         Agreement;

             (iii) in connection with any underwritten offering conducted
         pursuant to Section 6 hereof, obtain opinions of counsel to the Company
         (which counsel and opinions (in form, scope and substance) shall be
         reasonably satisfactory to the Managing Underwriters) addressed to each
         Electing Holder participating in such underwritten offering and the
         underwriters, covering such matters as are customarily covered in
         opinions requested in primary underwritten offerings of equity and
         convertible debt securities and such other matters as may be reasonably
         requested by such Electing Holders and underwriters (it being agreed
         that the matters to be covered by such opinions shall include, without
         limitation, as of the date of the opinion and as of the Effective Time
         of the Shelf Registration Statement or most recent post-effective
         amendment thereto, as the case may be, the absence from the Shelf
         Registration Statement and the Prospectus, including the documents
         incorporated by reference therein, of an untrue statement of a material
         fact or the omission of a material fact required to be stated therein
         or necessary to make the statements therein not misleading;


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             (iv) in connection with any underwritten offering conducted
         pursuant to Section 6 hereof, obtain "cold comfort" letters and updates
         thereof from the independent public accountants of the Company (and, if
         necessary, from the independent public accountants of any subsidiary of
         the Company or of any business acquired by the Company for which
         financial statements and financial data are, or are required to be,
         included in the Shelf Registration Statement), addressed to each
         Electing Holder participating in such underwritten offering (if such
         Electing Holder has provided such letter, representations or
         documentation, if any, required for such cold comfort letter to be so
         addressed) and the underwriters, in customary form and covering matters
         of the type customarily covered in "cold comfort" letters in connection
         with primary underwritten offerings;

             (v) in connection with any underwritten offering conducted pursuant
         to Section 6 hereof, deliver such documents and certificates as may be
         reasonably requested by any Electing Holders participating in such
         underwritten offering and the Managing Underwriters, if any, including,
         without limitation, certificates to evidence compliance with Section
         3(j) hereof and with any conditions contained in the underwriting
         agreement or other agreements entered into by the Company.

         (q) The Company will use its reasonable best efforts to cause the
Common Stock issuable upon conversion of the Securities to be listed on the
Nasdaq National Stock Market or other stock exchange or trading system on which
the Common Stock primarily trades on or prior to the Effective Time of the Shelf
Registration Statement hereunder.

         (r) In the event that any broker-dealer registered under the Exchange
Act shall be an "affiliate" (as defined in Rule 2720(b)(1) of the NASD Rules (or
any successor provision thereto)) of the Company or has a "conflict of interest"
(as defined in Rule 2720(b)(7) of the NASD Rules (or any successor provision
thereto)) and such broker-dealer shall underwrite, participate as a member of an
underwriting syndicate or selling group or assist in the distribution of any
Registrable Securities covered by the Shelf Registration Statement, whether as a
Holder of such Registrable Securities or as an underwriter, a placement or sales
agent or a broker or dealer in respect thereof, or otherwise, the Company shall
assist such broker-dealer in complying with the requirements of the NASD Rules,
including, without limitation, by (A) engaging a "qualified independent
underwriter" (as defined in Rule 2720(b)(15) of the NASD Rules (or any successor
provision thereto)) to participate in the preparation of the registration
statement relating to such Registrable Securities, to exercise usual standards
of due diligence in respect thereto and to recommend the public offering price
of such Registrable Securities, (B) indemnifying such qualified independent
underwriter to the extent of the indemnification of underwriters provided in
Section 5 hereof, and (C) providing such information to such broker-dealer as
may be required in order for such broker-dealer to comply with the requirements
of the NASD Rules.


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         (s) The Company shall use its reasonable best efforts to take all other
steps necessary to effect the registration, offering and sale of the Registrable
Securities covered by the Shelf Registration Statement contemplated hereby.

         4. Registration Expenses. Except as otherwise provided in Section 3,
the Company shall bear all fees and expenses incurred in connection with the
performance of its obligations under Sections 2, 3 and 6 hereof and shall bear
or reimburse the Electing Holders for the reasonable fees and documented
disbursements of a single counsel selected by a plurality of all Electing
Holders who own an aggregate of not less than 25% of the Registrable Securities
covered by the Shelf Registration Statement to act as counsel therefore in
connection with the Shelf Registration Statement. Each Electing Holder shall pay
all underwriting discounts and commissions and transfer taxes, if any, relating
to the sale or disposition of such Electing Holder's Registrable Securities
pursuant to the Shelf Registration Statement.

         5. Indemnification and Contribution.

         (a) Indemnification by the Company. Upon the registration of the
Registrable Securities pursuant to Section 2 hereof, the Company shall indemnify
and hold harmless each Electing Holder and each underwriter, selling agent or
other securities professional, if any, which facilitates the disposition of
Registrable Securities, and each of their respective officers and directors and
each person who controls such Electing Holder, underwriter, selling agent or
other securities professional within the meaning of Section 15 of the Securities
Act or Section 20 of the Exchange Act (each such person being sometimes referred
to as an "Indemnified Person") against any losses, claims, damages or
liabilities, joint or several, to which such Indemnified Person may become
subject under the Securities Act or otherwise, insofar as such losses, claims,
damages or liabilities (or actions in respect thereof) arise out of or are based
upon an untrue statement or alleged untrue statement of a material fact
contained in any Shelf Registration Statement under which such Registrable
Securities are to be registered under the Securities Act, or any Prospectus
contained therein or furnished by the Company to any Indemnified Person, or any
amendment or supplement thereto, or arise out of or are based upon the omission
or alleged omission to state therein a material fact required to be stated
therein or necessary to make the statements therein not misleading, and the
Company hereby agrees to reimburse such Indemnified Person for any legal or
other expenses reasonably incurred by them in connection with investigating or
defending any such action or claim as such expenses are incurred; provided,
however, that the Company shall not be liable to any such Indemnified Person in
any such case to the extent that any such loss, claim, damage or liability
arises out of or is based upon an untrue statement or alleged untrue statement
or omission or alleged omission made in such Shelf Registration Statement or
Prospectus, or amendment or supplement, in reliance upon and in conformity with
written information furnished to the Company by such Indemnified Person
expressly for use therein.


                                       11
<PAGE>

         (b) Indemnification by the Electing Holders and any Agents and
Underwriters. Each Electing Holder agrees, as a consequence of the inclusion of
any of such Electing Holder's Registrable Securities in such Shelf Registration
Statement, and each underwriter, selling agent or other securities professional,
if any, which facilitates the disposition of Registrable Securities shall agree,
as a consequence of facilitating such disposition of Registrable Securities,
severally and not jointly, to (i) indemnify and hold harmless the Company, its
directors, officers who sign any Shelf Registration Statement and each person,
if any, who controls the Company within the meaning of either Section 15 of the
Securities Act or Section 20 of the Exchange Act, against any losses, claims,
damages or liabilities to which the Company or such other persons may become
subject, under the Securities Act or otherwise, insofar as such losses, claims,
damages or liabilities (or actions in respect thereof) arise out of or are based
upon an untrue statement or alleged untrue statement of a material fact
contained in such Shelf Registration Statement or Prospectus, or any amendment
or supplement, or arise out of or are based upon the omission or alleged
omission to state therein a material fact required to be stated therein or
necessary to make the statements therein not misleading, in each case to the
extent, but only to the extent, that such untrue statement or alleged untrue
statement or omission or alleged omission was made in reliance upon and in
conformity with written information furnished to the Company by such Electing
Holder, underwriter, selling agent or other securities professional expressly
for use therein, and (ii) reimburse the Company for any legal or other expenses
reasonably incurred by the Company in connection with investigating or defending
any such action or claim as such expenses are incurred.

         (c) Notices of Claims, Etc. Promptly after receipt by an indemnified
party under subsection (a) or (b) above of notice of the commencement of any
action, such indemnified party shall, if a claim in respect thereof is to be
made against an indemnifying party under this Section 5, notify such
indemnifying party in writing of the commencement thereof; but the omission so
to notify the indemnifying party shall not relieve it from any liability which
it may have to any indemnified party otherwise than under the indemnification
provisions of or contemplated by subsection (a) or (b) above. In case any such
action shall be brought against any indemnified party and it shall notify an
indemnifying party of the commencement thereof, such indemnifying party shall be
entitled to participate therein and, to the extent that it shall wish, jointly
with any other indemnifying party similarly notified, to assume the defense
thereof, with counsel reasonably satisfactory to such indemnified party (who
shall not, except with the consent of the indemnified party, be counsel to the
indemnifying party), and, after notice from the indemnifying party to such
indemnified party of its election so to assume the defense thereof, such
indemnifying party shall not be liable to such indemnified party under this
Section 5 for any legal expenses of other counsel or any other expenses, in each
case subsequently incurred by such indemnified party, in connection with the
defense thereof other than reasonable costs of investigation. No indemnifying
party shall, without the written consent of the indemnified party, effect the
settlement or compromise of, or consent to the entry of any judgment with
respect to, any pending or threatened action or claim in respect of which
indemnification or contribution may be sought hereunder (whether or not the
indemnified party is an actual or potential party to such action or claim)
unless such settlement, compromise or judgment (i) includes an unconditional
release of the indemnified party from all liability arising out of such action
or claim and (ii) does not include a statement as to, or an admission of, fault,
culpability or a failure to act, by or on behalf of any indemnified party.


                                       12
<PAGE>

         (d) Contribution. If the indemnification provided for in this Section 5
is unavailable to or insufficient to hold harmless an indemnified party under
subsection (a) or (b) above in respect of any losses, claims, damages or
liabilities (or actions in respect thereof) referred to therein, then each
indemnifying party shall contribute to the amount paid or payable by such
indemnified party as a result of such losses, claims, damages or liabilities (or
actions in respect thereof) in such proportion as is appropriate to reflect the
relative fault of the indemnifying party and the indemnified party in connection
with the statements or omissions which resulted in such losses, claims, damages
or liabilities (or actions in respect thereof), as well as any other relevant
equitable considerations. The relative fault of such indemnifying party and
indemnified party shall be determined by reference to, among other things,
whether the untrue or alleged untrue statement of a material fact or omission or
alleged omission to state a material fact relates to information supplied by
such indemnifying party or by such indemnified party, and the parties' relative
intent, knowledge, access to information and opportunity to correct or prevent
such statement or omission. The parties hereto agree that it would not be just
and equitable if contribution pursuant to this Section 5(d) were determined by
pro rata allocation (even if the Electing Holders or any underwriters, selling
agents or other securities professionals or all of them were treated as one
entity for such purpose) or by any other method of allocation which does not
take account of the equitable considerations referred to in this Section 5(d).
The amount paid or payable by an indemnified party as a result of the losses,
claims, damages or liabilities (or actions in respect thereof) referred to above
shall be deemed to include any legal or other fees or expenses reasonably
incurred by such indemnified party in connection with investigating or defending
any such action or claim. No person guilty of fraudulent misrepresentation
(within the meaning of Section 11(f) of the Securities Act) shall be entitled to
contribution from any person who was not guilty of such fraudulent
misrepresentation. The obligations of the Electing Holders and any underwriters,
selling agents or other securities professionals in this Section 5(d) to
contribute shall be several in proportion to the percentage of principal amount
of Registrable Securities registered or underwritten, as the case may be, by
them and not joint.

         (e) Notwithstanding any other provision of this Section 5, in no event
will any (i) Electing Holder be required to undertake liability to any person
under this Section 5 for any amounts in excess of the dollar amount of the
proceeds to be received by such Holder from the sale of such Holder's
Registrable Securities (after deducting any fees, discounts and commissions
applicable thereto) pursuant to any Shelf Registration Statement under which
such Registrable Securities are to be registered under the Securities Act and
(ii) underwriter, selling agent or other securities professional be required to
undertake liability to any person hereunder for any amounts in excess of the
discount, commission or other compensation payable to such underwriter, selling
agent or other securities professional with respect to the Registrable
Securities underwritten by it and distributed to the public.

         (f) The obligations of the Company under this Section 5 shall be in
addition to any liability which the Company may otherwise have to any Electing
Holder and the obligations of any Electing Holder under this Section 5 shall be
in addition to any liability which such Electing Holder may otherwise have to
the Company. The remedies provided in this Section 5 are not exclusive and shall
not limit any rights or remedies which may otherwise be available to an
indemnified party at law or in equity.


                                       13
<PAGE>

         6. Underwritten Offering. Any Holder of Registrable Securities who
desires to do so may sell Registrable Securities (in whole or in part) in an
underwritten offering; provided that (i) the Electing Holders of at least
33-1/3% in aggregate principal amount of the Registrable Securities then covered
by the Shelf Registration Statement shall request such an offering and (ii) at
least such aggregate principal amount of such Registrable Securities shall be
included in such offering; and provided further that the Company shall not be
obligated to cooperate with more than one underwritten offering during the
Effectiveness Period. Upon receipt of such a request, the Company shall provide
all Holders of Registrable Securities written notice of the request, which
notice shall inform such Holders that they have the opportunity to participate
in the offering. In any such underwritten offering, the investment banker or
bankers and manager or managers that will administer the offering will be
selected by, and the underwriting arrangements with respect thereto (including
the size of the offering) will be approved by, the holders of a majority of the
Registrable Securities to be included in such offering; provided, however, that
such investment bankers and managers and underwriting arrangements must be
reasonably satisfactory to the Company. No Holder may participate in any
underwritten offering contemplated hereby unless (a) such Holder agrees to sell
such Holder's Registrable Securities to be included in the underwritten offering
in accordance with any approved underwriting arrangements, (b) such Holder
completes and executes all reasonable questionnaires, powers of attorney,
indemnities, underwriting agreements, lock-up letters and other documents
required under the terms of such approved underwriting arrangements, and (c) if
such Holder is not then an Electing Holder, such Holder returns a completed and
signed Notice and Questionnaire to the Company in accordance with Section
3(a)(ii) hereof within a reasonable amount of time before such underwritten
offering. The Holders participating in any underwritten offering shall be
responsible for any underwriting discounts and commissions and fees and, subject
to Section 4 hereof, expenses of their own counsel. The Company shall pay all
expenses customarily borne by issuers in an underwritten offering, including but
not limited to filing fees, the fees and disbursements of its counsel and
independent public accountants and any printing expenses incurred in connection
with such underwritten offering. Notwithstanding the foregoing or the provisions
of Section 3(n) hereof, upon receipt of a request from the Managing Underwriter
or a representative of Holders of a majority of the Registrable Securities to be
included in an underwritten offering to prepare and file an amendment or
supplement to the Shelf Registration Statement and Prospectus in connection with
an underwritten offering, the Company may delay the filing of any such amendment
or supplement for up to 90 days if the Board of Directors of the Company shall
have determined in good faith that the Company has a bona fide business reason
for such delay.

         7. Additional Interest.

         (a) Notwithstanding any postponement of effectiveness permitted by
Section 2(a) hereof, if (i) a Shelf Registration Statement has not been filed
with the Commission on or prior to the 90th day following the Closing Date, if
at such time the Company is eligible to file a registration statement on Form
S-3 or, if the Company is not eligible to file a registration statement on Form
S-3 at such time, the 135th day after the Closing Date, or (ii) the Shelf
Registration Statement is not declared effective by the Commission on or prior
to the 180th day following the Closing Date, if the Company is required to file
a Shelf Registration Statement covering resales of Registrable Securities within
90 calendar days after the Closing Date or the 225th day after the Closing Date
if the Company is required to file such Shelf Registration Statement on or prior
to the 135th calendar day after the Closing date (each, a "Registration
Default"), the Company shall be required to pay additional interest ("Additional
Interest"), from and including the day following such Registration Default until
such Shelf Registration Statement is either so filed or so filed and
subsequently declared effective, as applicable, at a rate per annum equal to an
additional one-quarter of one percent (0.25%) of the principal amount of
Registrable Securities, to and including the 90th day following such
Registration Default and one-half of one percent (0.50%) thereof from and after
the 91st day following such Registration Default.


                                       14
<PAGE>

         (b) In the event that (i) the Shelf Registration Statement ceases to be
effective when so required to be effective, (ii) the Company suspends the use of
the Prospectus pursuant to Section 2(c) or 3(j) hereof, (iii) the Holders are
not authorized to use the Prospectus pursuant to Section 3(g) hereto or (iv) the
Holders are otherwise prevented or restricted by the Company from effecting
sales pursuant to the Shelf Registration Statement (an "Effective Failure") for
more than 30 days, whether or not consecutive, in any 90-day period, or for more
than 90 days, whether or not consecutive, during any 12-month period, then the
Company shall pay Additional Interest at a rate per annum equal to an additional
one-quarter of one pecent (0.25%) of the principal amount of the Registrable
Securities for the first 90 days after the occurrence of the event and an amount
equal to one-half of one percent (0.50%) of the principal amount of Registrable
Securities from the 91st day after the occurrence of the event until the earlier
of (1) the time the Holders of Registrable Securities are again able to make
sales under the Shelf Registration Statement or (2) the expiration of the
Effectiveness Period.

         (c) Notwithstanding the foregoing, in no event will Additional Interest
be payable in connection with a failure to register the Common Stock. For the
avoidance of doubt, if the Company fails to register both the Securities and the
Common Stock, then the Additional Interest shall be payable in connection with
the failure to register the Securities.

         (d) Any amounts to be paid as Additional Interest pursuant to
paragraphs (a) or (b) of this Section 7 shall be paid in cash semi-annually in
arrears, with the first semi-annual payment due on the first [Interest Payment
Date] (as defined in the Indenture), as applicable, following the date of such
Registration Default or Effective Failure, as applicable. Such Additional
Interest will accrue in respect of the Securities at the rates set forth in
paragraphs (a) or (b) of this Section 7, as applicable, on the principal amount
of the Securities.

         (e) Except as provided in Section 8(b) hereof, the Additional Interest
as set forth in this Section 7 shall be the exclusive monetary remedy available
to the Holders of Securities for such Registration Default or Effective Failure.
In no event shall the Company be required to pay Additional Interest in excess
of the applicable maximum amount of one-half of one percent (0.50%) set forth
above, regardless of whether one or multiple Registration Defaults or Effective
Failures exist.


                                       15
<PAGE>

         8. Miscellaneous.

         (a) Other Registration Rights. The Company may grant registration
rights that would permit any person that is a third party the right to
piggy-back on any Shelf Registration Statement, provided that if the Managing
Underwriter of any underwritten offering conducted pursuant to Section 6 hereof
notifies the Company and the Electing Holders that the total amount of
securities which the Electing Holders and the holders of such piggy-back rights
intend to include in any Shelf Registration Statement is so large as to
materially threaten the success of such offering (including the price at which
such securities can be sold), then the amount, number or kind of securities to
be offered for the account of holders of such piggy-back rights will be reduced
to the extent necessary to reduce the total amount of securities to be included
in such offering to the amount, number and kind recommended by the Managing
Underwriter prior to any reduction in the amount of Registrable Securities to be
included in such Shelf Registration Statement.

         (b) Specific Performance. The parties hereto acknowledge that there
would be no adequate remedy at law if the Company fails to perform any of its
obligations hereunder and that the Purchasers and the Holders from time to time
may be irreparably harmed by any such failure, and accordingly agree that the
Purchasers and such Holders, in addition to any other remedy to which they may
be entitled at law or in equity and without limiting the remedies available to
the Electing Holders under Section 7 hereof, shall be entitled to compel
specific performance of the obligations of the Company under this Registration
Rights Agreement in accordance with the terms and conditions of this
Registration Rights Agreement, in any court of the United States or any State
thereof having jurisdiction.

         (c) Amendments and Waivers. This Agreement, including this Section
8(c), may be amended, and waivers or consents to departures from the provisions
hereof may be given, only by a written instrument duly executed by the Company
and the Holders of a majority in aggregate principal amount of Registrable
Securities then outstanding. Each Holder of Registrable Securities outstanding
at the time of any such amendment, waiver or consent or thereafter shall be
bound by any amendment, waiver or consent effected pursuant to this Section
8(c), whether or not any notice, writing or marking indicating such amendment,
waiver or consent appears on the Registrable Securities or is delivered to such
Holder.

         (d) Notices. All notices and other communications provided for or
permitted hereunder shall be given as provided in the Indenture.

         (e) Parties in Interest. The parties to this Agreement intend that all
Holders of Registrable Securities shall be entitled to receive the benefits of
this Agreement and that any Electing Holder shall be bound by the terms and
provisions of this Agreement by reason of such election with respect to the
Registrable Securities which are included in a Shelf Registration Statement. All
the terms and provisions of this Agreement shall be binding upon, shall inure to
the benefit of and shall be enforceable by the respective successors and assigns
of the parties hereto and any Holder from time to time of the Registrable
Securities to the aforesaid extent. In the event that any transferee of any
Holder of Registrable Securities shall acquire Registrable Securities, in any
manner, whether by gift, bequest, purchase, operation of law or otherwise, such
transferee shall, without any further writing or action of any kind, be entitled
to receive the benefits of and, if an Electing Holder, be conclusively deemed to
have agreed to be bound by and to perform all of the terms and provisions of
this Agreement to the aforesaid extent.


                                       16
<PAGE>

         (f) Counterparts. This Agreement may be executed in any number of
counterparts and by the parties hereto in separate counterparts, each of which
when so executed shall be deemed to be an original and all of which taken
together shall constitute one and the same agreement.

         (g) Headings. The headings in this Agreement are for convenience of
reference only and shall not limit or otherwise affect the meaning hereof.

         (h) Governing Law. This Agreement shall be governed by and construed in
accordance with the laws of the State of New York.

         (i) Severability. In the event that any one or more of the provisions
contained herein, or the application thereof in any circumstances, is held
invalid, illegal or unenforceable in any respect for any reason, the validity,
legality and enforceability of any such provision in every other respect and of
the remaining provisions hereof shall not be in any way impaired or affected
thereby, it being intended that all of the rights and privileges of the parties
hereto shall be enforceable to the fullest extent permitted by law.

         (j) Survival. The respective indemnities, agreements, representations,
warranties and other provisions set forth in this Agreement or made pursuant
hereto shall remain in full force and effect, regardless of any investigation
(or any statement as to the results thereof) made by or on behalf of any
Electing Holder, any director, officer or partner of such Holder, any agent or
underwriter, any director, officer or partner of such agent or underwriter, or
any controlling person of any of the foregoing, and shall survive the transfer
and registration of the Registrable Securities of such Holder.



                                       17
<PAGE>



         Please confirm that the foregoing correctly sets forth the agreement
between the Company and you.

                                           Very truly yours,

                                           ENZON PHARMACEUTICALS, INC.


                                           By:  /S/ JEFFREY H. BUCHALTER
                                              --------------------------------

                                                Name:  Jeffrey H. Buchalter
                                                Title: Chairman, President & CEO

Accepted as of the date hereof:
GOLDMAN, SACHS & CO.


By:       /s/ GOLDMAN, SACHS & CO.
   --------------------------------------------------

             (Goldman, Sachs & Co.)
             On behalf of each of the Purchasers





                                       18
<PAGE>



                                                                      APPENDIX A



                           Enzon Pharmaceuticals, Inc.


                         INSTRUCTION TO DTC PARTICIPANTS

                                (Date of Mailing)

                     URGENT - IMMEDIATE ATTENTION REQUESTED

                           DEADLINE FOR RESPONSE: [ ]


                  The Depository Trust Company ("DTC") has identified you as a
DTC Participant through which beneficial interests in the Enzon Pharmaceuticals,
Inc. (the "Company) 4% Convertible Senior Notes due 2013 (the "Securities") are
held.

                  The Company is in the process of registering the Securities
under the Securities Act of 1933 for resale by the beneficial owners thereof. In
order to have their Securities included in the registration statement,
beneficial owners must complete and return the enclosed Notice of Registration
Statement and Selling Securityholder Questionnaire.

                  It is important that beneficial owners of the Securities
receive a copy of the enclosed materials as soon as possible as their rights to
have the Securities included in the registration statement depend upon their
returning the Notice and Questionnaire by [ ]. Please forward a copy of the
enclosed documents to each beneficial owner that holds interests in the
Securities through you. If you require more copies of the enclosed materials or
have any questions pertaining to this matter, please contact [Investor
Relations], 685 Route 202/206, Bridgewater, New Jersey 08807.


<PAGE>



                           Enzon Pharmaceuticals, Inc.


                        Notice of Registration Statement
                                       and
                      Selling Securityholder Questionnaire


                                     [Date]


                  Enzon Pharmaceuticals, Inc. (the "Company") has filed with the
United States Securities and Exchange Commission (the "Commission") a
registration statement on [Form S-1] [Form S-3] (the "Shelf Registration
Statement") for the registration and resale under Rule 415 of the United States
Securities Act of 1933, as amended (the "Securities Act"), of the Company's 4%
Convertible Senior Notes due 2013 (the "Securities") and the shares of common
stock, par value $0.01 per share (the "Common Stock"), issuable upon conversion
thereof, in accordance with the Registration Rights Agreement, dated as of
May 23, 2006 (the "Registration Rights Agreement"), between the Company and the
purchasers named therein. A copy of the Registration Rights Agreement is
attached hereto. All capitalized terms not otherwise defined herein shall have
the meanings ascribed thereto in the Registration Rights Agreement.

                  In order to have Registrable Securities included in the Shelf
Registration Statement (or a supplement or amendment thereto), this Notice of
Registration Statement and Selling Securityholder Questionnaire ("Notice and
Questionnaire") must be completed, executed and delivered to the Company at the
address set forth herein for receipt ON OR BEFORE [DEADLINE FOR RESPONSE].
Beneficial owners of Registrable Securities who do not complete, execute and
return this Notice and Questionnaire by such date (i) will not be named as
selling securityholders in the Shelf Registration Statement and (ii) may not use
the Prospectus forming a part thereof for resales of Registrable Securities.

                  Certain legal consequences arise from being named as a selling
securityholder in the Shelf Registration Statement and related Prospectus.
Accordingly, holders and beneficial owners of Registrable Securities are advised
to consult their own securities law counsel regarding the consequences of being
named or not being named as a selling securityholder in the Shelf Registration
Statement and related Prospectus.



                                       20
<PAGE>



                  The term "Registrable Securities" is defined in the
Registration Rights Agreement to mean all or any portion of the Securities
issued on May 23, 2006 under the Indenture in registered form and the shares of
Common Stock issuable upon conversion of such Securities; provided, however,
that a security ceases to be a Registrable Security when it is no longer a
Restricted Security.

                  The term "Restricted Security" is defined in the Registration
Rights Agreement to mean any Security or share of Common Stock issuable upon
conversion thereof except any such Security or share of Common Stock which (i)
has been effectively registered under the Securities Act and sold in a manner
contemplated by the Shelf Registration Statement, (ii) has been transferred in
compliance with Rule 144 under the Securities Act (or any successor provision
thereto) or is transferable pursuant to paragraph (k) of such Rule 144 (or any
successor provision thereto), or (iii) has otherwise been transferred and a new
Security or share of Common Stock not subject to transfer restrictions under the
Securities Act has been delivered by or on behalf of the Company in accordance
with Section 2.1 of the Indenture.

                                    ELECTION

                  The undersigned holder (the "Selling Securityholder") of
Registrable Securities hereby elects to include in the Shelf Registration
Statement the Registrable Securities beneficially owned by it and listed below
in Item (3). The undersigned, by signing and returning this Notice and
Questionnaire, agrees to be bound with respect to such Registrable Securities by
the terms and conditions of this Notice and Questionnaire and the Registration
Rights Agreement, including, without limitation, Section 5 of the Registration
Rights Agreement, as if the undersigned Selling Securityholder were an original
party thereto.

                  Upon any sale of Registrable Securities pursuant to the Shelf
Registration Statement, the Selling Securityholder will be required to deliver
to the Company and the Trustee the Notice of Transfer (completed and signed) set
forth in Exhibit 1 to this Notice and Questionnaire.

                  The Selling Securityholder hereby provides the following
information to the Company and represents and warrants that such information is
accurate and complete:



                                       21
<PAGE>



                                  QUESTIONNAIRE


(1)  (a)    Full Legal Name of Selling Securityholder:

            -------------------------------------------------------------------
     (b)    Full Legal Name of Registered Holder (if not the same as in (a)
            above) of Registrable Securities Listed in Item (3) Below:

            -------------------------------------------------------------------
     (c)    Full Legal Name of DTC Participant (if applicable and if not the
            same as (b) above) Through Which Registrable Securities Listed in
            Item (3) Below are Held:

            -------------------------------------------------------------------

(2)         Address for Notices to Selling Securityholder:

                                _______________________________________
                                _______________________________________
                                _______________________________________
            Telephone:          _______________________________________
            Fax:                _______________________________________
            Contact Person:     _______________________________________


(3)         Beneficial Ownership of Securities:

            Except as set forth below in this Item (3), the undersigned Selling
            Securityholder does not beneficially own any Securities or shares of
            Common Stock issued upon conversion, repurchase or redemption of any
            Securities.

     (a)    Principal amount of Securities constituting Registrable Securities
            beneficially owned: CUSIP No(s). of such Registrable Securities:
            ____________________________________________________________________

            Number of shares of Common Stock Securities constituting Registrable
            Securities (if any): _______________________________________________

     (b)    Principal amount of Securities other than Registrable Securities
            beneficially owned: ________________________________________________
            CUSIP No(s). of such other Securities: _____________________________

            Number of shares of Common Stock (if any) issued upon conversion of
            such other Securities: _____________________________________________

     (c)    Principal amount of Registrable Securities which the undersigned
            wishes to be included in the Shelf Registration Statement:
            ____________________________________________________________________
            CUSIP No(s). of such Registrable Securities to be included in the
            Shelf Registration Statement: ______________________________________

            Number of shares of Common Stock (if any) constituting Registrable
            Securities which are to be included in the Shelf Registration
            Statement: _________________________________________________________


                                       22
<PAGE>

     (4)    Beneficial Ownership of Other Securities of the Company:

            Except as set forth below in this Item (4), the undersigned Selling
            Securityholder is not the beneficial or registered owner of any
            shares of Common Stock or any other securities of the Company, other
            than the Securities and shares of Common Stock listed above in Item
            (3).

            State any exceptions here:



     (5)    Relationships with the Company:

            Except as set forth below, neither the Selling Securityholder nor
            any of its affiliates, officers, directors or principal equity
            holders (5% or more) has held any position or office or has had any
            other material relationship with the Company (or its predecessors or
            affiliates) during the past three years.

            State any exceptions here:



     (6)    Plan of Distribution:

            Except as set forth below, the undersigned Selling Securityholder
            intends to distribute the Registrable Securities listed above in
            Item (3) only as follows (if at all): Such Registrable Securities
            may be sold from time to time directly by the undersigned Selling
            Securityholder or, alternatively, through underwriters,
            broker-dealers or agents. Such Registrable Securities may be sold in
            one or more transactions at fixed prices, at prevailing market
            prices at the time of sale, at varying prices determined at the time
            of sale, or at negotiated prices. Such sales may be effected in
            transactions (which may involve crosses or block transactions) (i)
            on any national securities exchange or quotation service on which
            the Registrable Securities may be listed or quoted at the time of
            sale, (ii) in the over-the-counter market, (iii) in transactions
            otherwise than on such exchanges or services or in the
            over-the-counter market, or (iv) through the writing of options. In
            connection with sales of the Registrable Securities or otherwise,
            the Selling Securityholder may enter into hedging transactions with
            broker-dealers, which may in turn engage in short sales of the
            Registrable Securities in the course of hedging the positions they
            assume. The Selling Securityholder may also sell Registrable
            Securities short and deliver Registrable Securities to close out
            such short positions, or loan or pledge Registrable Securities to
            broker-dealers that in turn may sell such securities.

            State any exceptions here:



                   Note: In no event may such method(s) of distribution take the
form of an underwritten offering of the Registrable Securities without the prior
agreement of the Company.


                                       23
<PAGE>

                  By signing below, the Selling Securityholder acknowledges that
it understands its obligation to comply, and agrees that it will comply, with
the prospectus delivery and other provisions of the Securities Act and the
Exchange Act and the rules and regulations thereunder, particularly Regulation
M.

                  In the event that the Selling Securityholder transfers all or
any portion of the Registrable Securities listed in Item (3) above after the
date on which such information is provided to the Company, the Selling
Securityholder agrees to notify the transferee(s) at the time of the transfer of
its rights and obligations under this Notice and Questionnaire and the
Registration Rights Agreement.

                  By signing below, the Selling Securityholder consents to the
disclosure of the information contained herein in its answers to Items (1)
through (6) above and the inclusion of such information in the Shelf
Registration Statement and related Prospectus. The Selling Securityholder
understands that such information will be relied upon by the Company in
connection with the preparation of the Shelf Registration Statement and related
Prospectus.

                  In accordance with the Selling Securityholder's obligation
under Section 3(a) of the Registration Rights Agreement to provide such
information as may be required by law for inclusion in the Shelf Registration
Statement, the Selling Securityholder agrees to promptly notify the Company of
any inaccuracies or changes in the information provided herein which may occur
subsequent to the date hereof at any time while the Shelf Registration Statement
remains in effect. All notices hereunder and pursuant to the Registration Rights
Agreement shall be made in writing, by hand-delivery, first-class mail, or air
courier guaranteeing overnight delivery as follows:

           (i) To the Company:


                                                  -------------------------

                                                  -------------------------

                                                  -------------------------

                                                  -------------------------

                                                  -------------------------



           (ii) With a copy to:

                                                  -------------------------

                                                  -------------------------

                                                  -------------------------

                                                  -------------------------

                                                  -------------------------




                  Once this Notice and Questionnaire is executed by the Selling
Securityholder and received by the Company, the terms of this Notice and
Questionnaire, and the representations and warranties contained herein, shall be
binding on, shall inure to the benefit of and shall be enforceable by the
respective successors, heirs, personal representatives, and assigns of the
Company and the Selling Securityholder (with respect to the Registrable
Securities beneficially owned by such Selling Securityholder and listed in Item
(3) above). This Agreement shall be governed in all respects by the laws of the
State of New York.


                                       24
<PAGE>

                  IN WITNESS WHEREOF, the undersigned, by authority duly given,
has caused this Notice and Questionnaire to be executed and delivered either in
person or by its duly authorized agent.

Dated: _____________________________



                  ______________________________________________________________

                  Selling Securityholder
                  (Print/type full legal name of beneficial owner of Registrable
                  Securities)



                  By:  _________________________________________________________
                  Name:
                  Title:



PLEASE RETURN THE COMPLETED AND EXECUTED NOTICE AND QUESTIONNAIRE FOR RECEIPT ON
OR BEFORE [DEADLINE FOR RESPONSE] TO THE COMPANY AT:

                                    -------------------------

                                    -------------------------

                                    -------------------------

                                    -------------------------

                                    -------------------------







                                       25
<PAGE>



                                                                       EXHIBIT 1
                                                                   TO APPENDIX A


              NOTICE OF TRANSFER PURSUANT TO REGISTRATION STATEMENT

Enzon Pharmaceuticals, Inc.
685 Route 202/206
Bridgewater, New Jersey 08807

Attention:  Scott Waldman

Wilmington Trust Company
[Address of Trustee]

Attention:  [Corporate Trust Services]

                  Re:  Enzon Pharmaceuticals, Inc. (the "Company")
                       4% Convertible Senior Notes due 2013 (the "Notes")

Dear Sirs:

                  Please be advised that _____________________ has transferred
$___________ aggregate principal amount of the above-referenced Notes or shares
of the Company's common stock, issued upon conversion, repurchase or redemption
of Notes, pursuant to an effective Registration Statement on Form S-3 (File No.
333-____) filed by the Company.

                  We hereby certify that the prospectus delivery requirements,
if any, of the Securities Act of 1933, as amended, have been satisfied with
respect to the transfer described above and that the above-named beneficial
owner of the Notes or common stock is named as a selling securityholder in the
Prospectus dated [date], or in amendments or supplements thereto, and that the
aggregate principal amount of the Notes or number of shares of common stock
transferred are the Notes or shares of common stock listed in such Prospectus as
amended or supplemented opposite such owner's name.

Dated:

                                                        Very truly yours,

                                                        ________________________
                                                        (Name)

                                      By:               ________________________