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                                                                     EXHIBIT 4.4

THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE NOT BEEN REGISTERED UNDER
THE SECURITIES ACT OF 1933 OR ANY OTHER SECURITIES LAWS. THESE SECURITIES HAVE
BEEN ACQUIRED FOR INVESTMENT AND NOT WITH A VIEW TO DISTRIBUTION OR RESALE. SUCH
SECURITIES MAY NOT BE OFFERED FOR SALE, SOLD, DELIVERED AFTER SALE, TRANSFERRED,
PLEDGED OR HYPOTHECATED IN THE ABSENCE OF AN EFFECTIVE REGISTRATION STATEMENT
COVERING SUCH SECURITIES UNDER THE SECURITIES ACT OF 1933 AND ANY OTHER
APPLICABLE SECURITIES LAWS, UNLESS THE HOLDER SHALL HAVE OBTAINED AN OPINION OF
COUNSEL REASONABLY SATISFACTORY TO THE COMPANY THAT SUCH REGISTRATION IS NOT
REQUIRED.

                          MEMORY PHARMACEUTICALS CORP.

                   WARRANT TO PURCHASE SHARES OF COMMON STOCK

         THIS CERTIFIES that, for value received, Hoffmann-La Roche Inc., its
successors and permitted assigns (the "HOLDER"), is entitled, upon the terms and
subject to the conditions hereinafter set forth, to subscribe for and purchase
from Memory Pharmaceuticals Corp., a Delaware corporation with principal offices
at 100 Philips Parkway, Montvale, New Jersey 07645 (the "COMPANY"), Three
Hundred Forty-Seven Thousand Two Hundred Twenty-Two (347,222) fully paid and
nonassessable shares of the common stock, par value $.001 per share, of the
Company (the "COMMON STOCK" or the "SHARES"), at a price per share equal to
$4.32 (the "EXERCISE PRICE"), subject to the provisions and upon the terms and
conditions hereinafter set forth.

         1.       Method of Exercise; Payment.

                  (a)      Cash Exercise. The purchase rights represented by
this Warrant may be exercised by the Holder, in whole or in part, from time to
time on or after the date hereof and until 5:00 p.m. EST on September 11, 2008
by: (i) the surrender of this Warrant (with the notice of exercise form (the
"NOTICE OF EXERCISE") attached hereto as Exhibit A duly executed) at the
principal office of the Company; and (ii) by the payment to the Company of an
amount equal to the Exercise Price multiplied by the number of Shares being
purchased, which amount may be paid, at the election of the Holder, by wire
transfer or certified check payable to the order of the Company. The person or
persons in whose name(s) any certificate(s) representing Shares shall be
issuable upon exercise of this Warrant shall be deemed to have become the
holder(s) of record of, and shall be treated for all purposes as the record
holder(s) of, the Shares represented thereby (and such Shares shall be deemed to
have been issued) immediately prior to the close of business on the date or
dates upon which this Warrant is exercised.

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                  (b)      Net Issue Exercise. In lieu of exercising this
Warrant pursuant to Section 1(a) hereof, the Holder may elect, in whole or in
part, from time to time, on or after the date hereof and until 5:00 p.m. EST on
September 11, 2008 to receive a number of Shares equal to the value (as
determined below) of this Warrant (or the portion thereof being canceled) by
surrender of this Warrant at the principal office of the Company, together with
the Notice of Exercise in which Alternative No. 1(b) is initialed by the Holder.
In such event, the Company shall issue to the Holder a number of Shares computed
using the following formula:

         X = Y*(A-B)
             -------
                A

Where    X = the number of Shares to be issued to the Holder.

         Y = the number of Shares subject to this warrant.

         A = the fair market value of one share of Common Stock.

         B = the Exercise Price (as adjusted to the date of such calculation).

                  (c)      Fair Market Value. For purposes of this Section 1,
the fair market value of the Common Stock shall mean:

         (i)      if the Company's Common Stock is traded on a national
securities exchange, the average of the closing price each day over the ten (10)
trading day period prior to the surrender of this Warrant for exercise in
accordance with the terms hereof;

         (ii)     if the Company's Common Stock is actively traded over-the
counter, the average of the closing bid and asked prices quoted on the NASDAQ
system (or similar system) each day over the ten (10) trading day period prior
to the surrender of this Warrant for exercise in accordance with the terms
hereof; or

         (iii)    if this Warrant is being exercised in conjunction with a
public offering of the Company's equity securities, the per share price to the
public pursuant to such public offering; or

         (iv)     if at any time the Company's Common Stock is not listed on any
national securities exchange or quoted in the NASDAQ System or the
over-the-counter market, then as determined by the board of directors of the
Company in good faith.

                  (d)      Stock Certificates. In the event of any exercise of
the rights represented by this Warrant (whether pursuant to Section 1(a) or
1(b)), certificates for the Shares so purchased shall be delivered to the Holder
and, unless this Warrant has been fully exercised, a new Warrant representing
the Shares with respect to which this Warrant shall not have been exercised
shall also be issued to the Holder within such time.

                                      -2-
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         2.       Stock Fully Paid; Reservation of Shares. All of the Shares
issuable upon the exercise of the rights represented by this Warrant will, upon
issuance and receipt of the Exercise Price therefor, be fully paid and
nonassessable, and free from all preemptive rights, rights of first refusal or
first offer, taxes, liens and charges with respect to the issuance thereof.
During such time as this Warrant remains outstanding, the Company shall at all
times have authorized and reserved for issuance sufficient shares of its Common
Stock to provide for the exercise of the rights represented by this Warrant.

         3.       Adjustment of Exercise Price and Number of Shares. The number
and kind of Shares purchasable upon the exercise of this Warrant and the
Exercise Price therefor shall be subject to adjustment from time to time upon
the occurrence of certain events, as follows:

                  (a)      Stock Splits, Dividends and Combinations. In the
event that the Company shall at any time subdivide the outstanding shares of
Common Stock, or shall issue a stock dividend on its outstanding shares of
Common Stock, the number of Shares issuable upon exercise of this Warrant
immediately prior to such subdivision or to the issuance of such stock dividend
shall be proportionately increased, and the Exercise Price shall be
proportionately decreased, and in the event that the Company shall at any time
combine the outstanding shares of Common Stock, the number of Shares issuable
upon exercise of this Warrant immediately prior to such combination shall be
proportionately decreased, and the Exercise Price shall be proportionately
increased, effective at the close of business on the date of such subdivision,
stock dividend or combination, as the case may be.

                  (b)      Recapitalizations. If at any time or from time to
time there shall be a recapitalization of the Common Stock (other than a
subdivision, combination or merger or sale of assets transaction provided for
elsewhere in this Section 3), provision shall be made so that the Holder of this
Warrant will thereafter be entitled to receive upon exercise of this Warrant the
number of shares of stock or other securities or property of the Company to
which a holder of Common Stock would have been entitled on such
recapitalization. In any such case, appropriate adjustment shall be made in the
application of the provisions of this Section 3 with respect to the rights of
the Holder of this Warrant after the recapitalization to the end that the
provisions of this Section 3 (including adjustment of the Exercise Price then in
effect and the number of shares issuable upon exercise of this Warrant) shall be
applicable after that event in as nearly an equivalent manner as may be
practicable.

                  (c)      Merger. If at any time there shall occur (a) the
acquisition of the Company by another entity by means of any transaction or
series of related transactions (including, without limitation, any stock
acquisition, reorganization, merger or consolidation but excluding any sale of
stock for capital raising purposes) other than a transaction or series of
transactions in which the holders of the voting securities of the Company
outstanding immediately prior to such transaction continue to retain (either by
such voting securities remaining outstanding or by such voting securities being
converted into voting securities of the surviving entity), more than fifty
percent (50%) of the total voting power represented by the voting securities of
the Company or such surviving entity outstanding immediately after such
transaction or series of transactions; or (b) a sale of all or substantially all
of the assets of the Company (each, a "MERGER EVENT"), then as a part of such

                                      -3-
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Merger Event and as a condition thereto, lawful provision shall be made so that
the Holder shall thereafter be entitled to receive, upon exercise of this
Warrant, the number of shares of stock or other securities of the successor
corporation resulting from such Merger Event, equivalent in value to that which
would have been issuable if the Holder had exercised this Warrant immediately
prior to the Merger Event. In any such case, appropriate adjustment (as
determined in good faith by the Company's Board of Directors) shall be made in
the application of the provisions of this Warrant with respect to the rights and
interest of the Holder after the Merger Event to the end that the provisions of
this Warrant (including adjustments of the Exercise Price and number of Shares
purchasable) shall be applicable to the greatest extent possible.

                  (d)      Notices. Upon any adjustment of the Exercise Price
and any increase or decrease in the number of Shares purchasable upon the
exercise of this Warrant in accordance with Section 3 hereof, then, and in each
such case, the Company, as soon as practicable, shall give written notice
thereof to the Holder at the address of such Holder as shown on the books of the
Company which notice shall state the Exercise Price as adjusted and, if
applicable, the increased or decreased number of Shares purchasable upon the
exercise of this Warrant, setting forth in reasonable detail the method of
calculation of each. Any written notice by the Company required or permitted
hereunder shall be given by hand delivery or first class mail, postage prepaid,
addressed to the Holder at the address shown on the books of the Company for the
Holder.

         4.       Fractional Shares. No fractional shares of Common Stock will
be issued in connection with any exercise hereunder, but in lieu of such
fractional shares the Company shall make a cash payment therefor upon the basis
of the Exercise Price then in effect.

         5.       Representations and Warranties by the Company.

                  (a)      Due Authority. The execution and delivery by the
Company of this Warrant and the performance of all obligations of the Company
hereunder, including the issuance to the Holder of the right to acquire Shares,
have been duly authorized by all necessary corporate action on the part of the
Company. The issuance of this Warrant does not contravene any law or
governmental rule, regulation or order applicable to the Company, and does not
and will not contravene any provision of, or constitute a default under, any
indenture, mortgage, contract or other instrument to which the Company is a
party or by which it is bound. This Warrant constitutes a legal, valid and
binding agreement of the Company, enforceable in accordance with its respective
terms.

                  (b)      Consents and Approvals. No consent or approval of,
giving of notice to, registration with, or taking of any other action in respect
of any state, federal or other governmental authority or agency is required with
respect to the execution, delivery and performance by the Company of its
obligations under this Warrant, other than (i) the filing of notices pursuant to
Regulation D under the Securities Act of 1933, as amended (the "ACT"), and any
filing required by applicable state securities law, which filings shall be made
by the time required thereby, and (ii) in connection with the Hart-Scott-Rodino
Antitrust Improvements Act of 1976, as amended.

         6.       Representations and Warranties by the Holder. The Holder
represents and warrants to the Company as follows:

                                      -4-
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                  (a)      This Warrant and the shares of Common Stock issuable
hereunder (the "SECURITIES") are being acquired for the Holder's own account,
for investment and not with a view to, or for resale in connection with, any
distribution or public offering thereof within the meaning of the Act, and the
Holder has no present intention of selling or engaging in any public
distribution thereof pursuant to a registration or exemption.

                  (b)      The Holder understands that the Securities have not
been registered under the Act by reason of their issuance in a transaction
exempt from the registration and prospectus delivery requirements of the Act
pursuant to Section 4(2) thereof, and that they must be held by the Holder
indefinitely, and that the Holder must therefore bear the economic risk of such
investment indefinitely, unless a subsequent disposition thereof is registered
under the Act or is exempted from such registration.

                  (c)      The Holder has such knowledge and experience in
financial and business matters that it is capable of evaluating the merits and
risks of the purchase of the Securities and of protecting its interests in
connection therewith.

                  (d)      The Holder is able to bear the economic risk of the
purchase of the Shares pursuant to the terms of this Warrant.

         7.       Rights of Stockholders. Nothing contained herein shall confer
upon the Holder any of the rights of a stockholder of the Company or any right
to vote for the election of directors or upon any matter submitted to
stockholders at any meeting thereof, or to give or withhold consent to any
corporate action (whether upon any recapitalization, issuance of stock,
reclassification of stock, change of par value, consolidation, merger,
conveyance, or otherwise) or to receive notice of meetings, or to receive
dividends or subscription rights or otherwise until the Warrant shall have been
exercised and the Shares purchasable upon the exercise hereof shall have been
issued.

         8.       Miscellaneous.

                  (a)      This Warrant shall be governed by, and construed in
accordance with, the laws of the State of New Jersey, without regard to
principles of conflict of laws.

                  (b)      The headings in this Warrant are for purposes of
reference only, and shall not limit or otherwise affect any of the terms hereof.

                  (c)      The terms of this Warrant shall be binding upon and
shall inure to the benefit of any successors in interest of the Company or the
Holder.

                  (d)      This Warrant and the other documents delivered
pursuant hereto constitute the full and entire understanding and agreement
between the parties with regard to the subjects hereof and thereof.

                  (e)      The Company shall not, by amendment of its
certificate of incorporation or through any other means, directly or indirectly,
avoid or seek to avoid the observance or

                                      -5-
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performance of any of the terms of this Warrant and shall at all times in good
faith assist in the carrying out of all such terms and in the taking of all such
action as may be necessary or appropriate in order to protect the rights of the
holder of this Warrant against impairment.

                  (f)      Upon receipt of evidence reasonably satisfactory to
the Company of the loss, theft, destruction or mutilation of this Warrant and,
in the case of any such loss, theft or destruction, upon delivery of an
indemnity agreement reasonably satisfactory in form and amount to the Company
or, in the case of any such mutilation, upon surrender and cancellation of such
Warrant, the Company, at its expense, will execute and deliver to the holder of
record, in lieu thereof, a new Warrant of like date and tenor.

                  (g)      This Warrant and any provision hereof may be amended,
waived or terminated only by an instrument in writing signed by the Company and
the Holder.

                  (h)      This Warrant may be executed in counterparts, each of
which when so executed shall be deemed an original, but both of which when taken
together shall constitute one and the same instrument.

                  (i)      The Company acknowledges and agrees that the holder
of this Warrant is entitled to certain "incidental" registration rights with
respect to the Shares issuable upon exercise of this Warrant. The terms of such
registration rights are contained in Section 4 of that certain Fourth Amended
and Restated Investor Rights Agreement of even date herewith, by and among the
Company and the other parties thereto.

                            [SIGNATURE PAGE FOLLOWS]

                                      -6-
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         IN WITNESS WHEREOF, each of the Company and the Holder has caused this
Warrant to be signed by its duly authorized officer.

         Issued this 11 day of September, 2003.

                                    MEMORY PHARMACEUTICALS CORP.

                                    By: /s/ Tony Scullion
                                        -----------------------------------
                                        Name: Tony Scullion
                                        Title: CEO

                                    HOFFMANN-LA ROCHE INC.

                                    By: /s/ Frederick C. Kentz III
                                        -----------------------------------
                                        Name: Frederick C. Kentz III
                                        Title: Vice President & Secretary

                                      -7-
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                                    EXHIBIT A
                               NOTICE OF EXERCISE

TO:      Memory Pharmaceuticals Corp.
         Attention: President

Alternatives: Choose either 1(a) or 1(b).

         1(a). The undersigned hereby elects to purchase _______________ (leave
blank if you choose alternative No. 1(b) below) shares of Common Stock pursuant
to the terms of this Warrant, and tenders herewith payment of the purchase price
of such shares in full.

         1(b). In lieu of exercising the attached Warrant for cash or check, the
undersigned hereby elects to effect the net issuance provision of Section 1(b)
of this Warrant and receive ____________ (leave blank if you choose Alternative
No. 1(a) above) shares of Common Stock pursuant to the terms of this Warrant.
(Initial here if the undersigned elects this alternative).______________.

         2. Please issue a certificate or certificates representing said shares
of Common Stock in the name of the undersigned or in such other name as is
specified below:

                   ___________________________________________
                                     (Name)

                   ___________________________________________

                   ___________________________________________
                                    (Address)

         3. The undersigned hereby represents and warrants that the aforesaid
shares of Common Stock are being acquired for the account of the undersigned for
investment and not with a view to, or for resale, in connection with the
distribution thereof, and that the undersigned has no present intention of
distributing or reselling such shares except pursuant to a registration or
exemption, and all representations and warranties of the undersigned set forth
in Section 6 of the attached Warrant are true and correct as of the date hereof.

                                           By: _________________________________

                                           Name: _______________________________
                                                          (please print)

                                           Title: ______________________________

                                           Date: _______________________________