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                                                                    Exhibit 10.6


                            STOCK PURCHASE AGREEMENT


                  THIS AGREEMENT is made as of the 9th day of November, 2000,
between Cell Pathways, Inc. (the "Company"), a corporation organized under the
laws of the State of Delaware, with its principal offices at 702 Electronic
Drive, Horsham, Pennsylvania 19044 and each purchaser whose name is set forth on
the signature page hereof (each a "Purchaser" and collectively, the
"Purchasers").

                  IN CONSIDERATION of the mutual covenants contained in this
Agreement, the Company and each Purchaser, intending to be legally bound, agree
as follows:

                  SECTION 1. Authorization of Sale of the Units. Subject to the
terms and conditions of this Agreement, the Company has authorized the sale of
up to 3,200,000 units (the "Units"), each consisting of one share (each, a
"Share" and, collectively, the "Shares") of the common stock, $0.01 par value
per share, of the Company (the "Common Stock") and one warrant (each, a
"Warrant" and, collectively, the "Warrants"), to purchase one and thirty-five
hundredths (1.35) shares of common stock (each, a "Warrant Share" and,
collectively, the "Warrant Shares"). The terms of the Warrants shall be as set
forth in the form of Warrant set forth as Exhibit A attached hereto.

                  SECTION 2. Agreement to Sell and Purchase the Units. At the
Closing (as defined in Section 3), the Company will sell to each Purchaser, and
such Purchaser will buy from the Company, upon the terms and conditions
hereinafter set forth, the number of Units shown, and at the purchase price
shown, opposite such Purchaser's name on Schedule A attached hereto. The Shares
and the Warrants constituting the Units shall become immediately separable and
transferable upon the Closing. The Company may simultaneously enter into a
similar form of this purchase agreement with certain other investors (the "Other
Purchasers") and complete sales of Units to them, although it is understood that
there is no minimum number of Units that are required to be sold by the Company.
(The Purchaser and the Other Purchasers, if any, are hereinafter sometimes
collectively referred to as the "Purchasers," and this Agreement and the similar
agreements executed by the Other Purchasers are hereinafter sometimes
collectively referred to as the "Agreements.")

                  SECTION 3. Delivery of the Units at the Closing. The
completion of the purchase and sale of the Units (the "Closing") shall occur on
November 9, 2000, at the offices of Morgan, Lewis & Bockius LLP, 1701 Market
Street, Philadelphia, PA 19102, or at such other time or place as may be agreed
upon by the Company and each Purchaser (the "Closing Date"). At the Closing, the
Company shall deliver to such Purchaser one or more stock certificates for the
Shares and one or more Warrants registered in the name of such Purchaser, or in
such name(s) as designated by such Purchaser, based on the number of Units set
forth in Section 2





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above. The name(s) in which the stock certificates for the Shares and the
Warrants are to be registered are set forth in the Stock Certificate and Warrant
Questionnaire set forth on Appendix I attached hereto. The Company's obligation
to complete the purchase and sale of the Units and deliver such stock
certificate(s) and Warrant(s) to each Purchaser at the Closing shall be subject
to the following conditions, any one or more of which may be waived by the
Company in its sole discretion: (i) receipt by the Company of immediately
available funds in the full amount of the purchase price for the Units being
purchased hereunder; (ii) completion of the purchases and sales under the
Agreements with any Other Purchasers; and (iii) the accuracy of the
representations and warranties made by the Purchasers and the fulfillment of
those undertakings of the Purchasers to be fulfilled prior to the Closing;
provided, however, that in the event that condition (ii) or, with respect to
Other Purchasers, condition (iii) is not met, each Purchaser shall have the
right, but not the obligation, to purchase the Units which such Other Purchaser
(the "Defaulting Purchaser") should have purchased on the same terms, and if
Other Purchasers want to exercise this right, on a pro rata basis (based on the
number of Units purchased hereunder and under the other purchase agreements)
with any Other Purchasers exercising the right, and if the Purchaser and/or
Other Purchasers exercise this right, the condition shall be deemed to have been
met. Each Purchaser's obligation to accept delivery of such stock certificate(s)
and Warrant(s) and to pay for the Units evidenced thereby shall be subject to
the accuracy in all material respects of the representations and warranties made
by the Company in the Purchase Agreement and the fulfillment in all material
respects of those undertakings of the Company to be fulfilled prior to Closing.

                  SECTION 4. Representations, Warranties and Covenants of the
Company. The Company hereby represents and warrants to, and covenants with, each
Purchaser as follows:

                  4.1. Organization and Qualification. The Company is a
corporation duly organized and in good standing under the laws of the State of
Delaware and has all requisite corporate power and authority to conduct its
business as currently conducted. The Company is qualified to do business as a
foreign corporation and is in good standing in each jurisdiction in which the
Company conducts business, except where the failure to be so organized or in
good standing would not be reasonably likely to have a material adverse effect
on the business, condition (financial or otherwise) or results of operations of
the Company.

                  4.2. Authorized and Issued Capital Stock.

                  (a) As of September 30, 2000, the authorized capital stock of
the Company consists of (i) 150,000,000 shares of Common Stock, of which
27,873,457 shares were issued and outstanding, and (ii) 10,000,000 shares of
preferred stock, par value $0.01 per share, of which no shares are issued and
outstanding. Holders of the shares of Common Stock have certain rights pursuant
to the terms of a Rights Agreement, dated as of December 3, 1998, between the
Company and Registrar and Transfer Company, as rights agent. All of the
outstanding shares of Common Stock were validly issued and are fully paid and
non-assessable shares.



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                  (b) The Company has registered the Common Stock pursuant to
Section 12(g) of the Securities Exchange Act of 1934, as amended (together with
the rules and regulations promulgated thereunder, the "Exchange Act"), and, to
the date hereof, has filed all periodic reports required to be filed under the
Exchange Act. The Common Stock is currently included for listing in the Nasdaq
National Market.

                  4.3. Due Execution, Delivery and Performance of this
Agreement. The execution, delivery and performance of this Agreement by the
Company, including, without limitation, the issuance of the Shares and the
Warrants (i) have been duly authorized by all requisite corporate action by the
Company and (ii) will not violate (A) the Certificate of Incorporation (the
"Certificate of Incorporation") or the Bylaws (the "Bylaws") of the Company, (B)
any law, statute, rule or regulation applicable to the Company, or (C) any
provision of any material indenture, mortgage, agreement, contract or other
material instrument to which the Company is a party or by which the Company or
any of its properties or assets is bound as of the date hereof, and (iii) will
not result in a breach of or constitute (upon notice or lapse of time or both) a
default under any such material indenture, mortgage, agreement, contract or
other material instrument or result in the creation or imposition of any lien,
security interest, mortgage, pledge, charge or other encumbrance, of any
material nature whatsoever, upon any properties or assets of the Company, except
for such violations (other than in the case of clause (ii)(A)), breaches,
defaults or encumbrances which would not be reasonably likely to have a material
adverse effect on the business, condition (financial or otherwise) or results of
operations of the Company. The Company has no material subsidiaries, except Cell
Pathways Pharmaceuticals, Inc. Upon execution and delivery, and assuming the
valid execution thereof by the respective Purchasers, this Agreement will
constitute a valid and binding obligation of the Company, enforceable in
accordance with its terms, except as may be limited by applicable bankruptcy,
insolvency, reorganization, moratorium or similar laws affecting creditors' and
contracting parties' rights generally and except as enforceability may be
subject to general principles of equity (regardless of whether such
enforceability is considered in a proceeding in equity or at law) and except as
the indemnification and contribution agreements of the Company in Section 7.4
hereof may be legally unenforceable.

                  4.4. Issuance, Sale and Delivery of the Shares and Warrant
Shares. When issued and paid for, the Shares to be sold hereunder by the Company
and the Warrant Shares to be acquired upon exercise of the Warrants will be
validly issued and outstanding, fully paid and non-assessable. Neither the sale
of the Shares and Warrants, nor the Company's performance of its obligations
pursuant to this Agreement and the Warrants shall (i) result in the creation or
imposition of any liens, charges, claims or other encumbrances upon the Shares
or Warrants or any of the assets of the Company, or (ii) entitle the holders of
the outstanding Common Stock to preemptive or other similar rights to subscribe
to or acquire Common Stock or other securities of the Company.



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                  4.5. Exemption from Registration. Assuming the accuracy of
each Purchaser's representations and warranties set forth in Section 5 hereof,
the offer, issuance and sale of the Shares pursuant to this Agreement are and
will be exempt from the registration and prospectus delivery requirements of the
Securities Act of 1933, as amended (together with the rules and regulations
promulgated thereunder, the "Securities Act").

                  4.6. Additional Information. The Company represents and
warrants that the information contained in the following documents, copies of
which have been furnished to each Purchaser, was true and correct in all
material respects and did not contain any untrue statement of a material fact or
omit to state any material fact necessary to make the statements contained
therein in light of the circumstances under which they were made not misleading,
in each case as of their respective dates (the "SEC Documents"):

                  (i)      the Company's Annual Report on Form 10-K for the
                           fiscal year ended December 31, 1999 (without
                           exhibits);

                  (ii)     the Company's Quarterly Reports on Form 10-Q for the
                           three-month periods ended March 31, 2000, June 30,
                           2000 and September 30, 2000;

                  (iii)    the Company's Current Report on Form 8-K filed with
                           the Securities and Exchange Commission (the
                           "Commission") on September 29, 2000; and

                  (iv)     the notice of annual meeting of stockholders and
                           proxy statement for the Company's 2000 annual meeting
                           of stockholders held May 31, 2000.

                  4.7. No Material Change. As of the date hereof, to the
knowledge of the Company, there has been no undisclosed material adverse change
in the business, condition (financial or otherwise) or results of operations of
the Company since September 30, 2000, it being understood that (a) the Company
has not achieved revenues and that the continued expenditure of resources in the
Company's continuing operations does not constitute a material adverse change
within the meaning of this paragraph, and (b) that the Company is engaged in
ongoing projects and processes whose outcomes are uncertain and that the ongoing
developments in respect of these projects and processes do not constitute a
material adverse change within the meaning of this paragraph. By way of example
and not by way of limitation, the ongoing projects and processes whose outcomes
are uncertain include (i) the ongoing clinical trials of Aptosyn(TM) (exisulind)
and CP 461; (ii) the clinical trial of exisulind in sporadic colonic polyps (the
treatment portion has been completed and for which the blind has not been
broken) which trial, even if successful, will not be adequate evidence of
efficacy to file an NDA for use of Aptosyn in treatment of sporadic colonic
polyps and, even if successful, may not be supportive of the pending NDA for use
in FAP; (iii) the NDA for exisulind for familial adenomatous polypsis which was
submitted by the Company in August 1999, and with respect to which the FDA
issued a "not approvable" letter on September 25, 2000; (iv) the pendency of
patent applications in the patent offices of the United States and other
countries; (v) the pendency of





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certain class actions filed against the Company, as described most recently in
the notes to the financial statements included as part of the Company's
Quarterly Report on Form 10-Q for the quarter ended September 30, 2000, which
class actions are subject to developments that cannot be predicted by the
Company; and (vi) and the collaborations with major pharmaceutical companies for
combination therapy trials which are subject to change, delay or cancellation
due to any one or more factors which may develop at any time.

                   4.8. Legal Opinion. Prior to and as a condition to the
Closing, Morgan, Lewis & Bockius, LLP, counsel to the Company, will deliver a
legal opinion to the Purchasers as to the valid issuance of the Shares and the
Warrant Shares, a draft of which has been provided to the Purchasers prior to
the date hereof.

                  4.9. Listing of Common Stock. The Company shall use its best
commercially practical efforts to cause the Shares and the Warrant Shares to be
included for listing in the Nasdaq National Market and to maintain the listing
of the Shares and the Warrant Shares on each national securities exchange or
automated quotation system, if any, upon which shares of Common Stock are then
listed.

                  4.10 Eligibility. The Company is currently eligible to
register the resale of the Shares and the Warrant Shares on a registration
statement on Form S-3 under the Securities Act.


                   SECTION 5. Representations, Warranties and Covenants of the
Purchasers.

                  (a) Each Purchaser acknowledges that the offering and sale of
the Shares and Warrants have not been registered under the Securities Act or any
state securities law and that neither the Shares nor Warrants may be offered,
sold, pledged or otherwise transferred (i) in the absence of such registration,
(ii) unless the Company receives an opinion of counsel reasonably acceptable to
it that such offer, sale, pledge or transfer is exempt from any registration and
prospectus delivery requirements of the Securities Act and any applicable state
securities laws or (iii) unless the Shares or the Warrant Shares, as the case
may be, are sold pursuant to Rule 144 promulgated under the Securities Act
("Rule 144") in accordance with the terms of such rule. Except as otherwise
permitted by Section 7.3, each certificate for the Shares issued at the Closing,
or the Warrant Shares, as the case may be, or upon direct or indirect transfer
of or in substitution thereof, shall be stamped or otherwise imprinted with a
legend in substantially the following form:

                  The Shares represented by this certificate have not been
                  registered under the Securities Act of 1933, as amended, or
                  under any applicable state securities laws and may not be
                  offered, sold, pledged or transferred in the absence of such
                  registration unless the Company receives an opinion of
                  counsel, in form, substance and scope reasonably acceptable to
                  the Company, that such offer, sale,





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                  pledge or transfer is exempt from any registration and
                  prospectus delivery requirements of the Securities Act and
                  such applicable state securities laws.

                  Each Purchaser acknowledges and agrees that the Warrants will
contain a similar legend, as set forth on the top of the form of Warrant set
forth in Exhibit A.

                  (b) Each Purchaser represents and warrants, as of the date
hereof and as of the Closing Date, to, and covenants with, the Company that: (i)
the Purchaser is knowledgeable, sophisticated and experienced in making, and is
qualified to make, decisions with respect to investments in equity securities
presenting an investment decision like that involved in the purchase of the
Units, including investments in equity securities issued by development-stage
biopharmaceutical companies; (ii) the Purchaser or its counsel, accountants or
other investment advisers have requested, received, reviewed and considered all
information deemed relevant by them in making an informed decision to purchase
the Units, (iii) the Purchaser is acquiring the Units for its own account for
investment only and with no present intention of distributing any of the Units,
and there is no arrangement or understanding with any other persons regarding
the distribution of the Units; provided however, that such representation and
warranty will not limit the Purchaser's right to sell Shares or Warrant Shares
pursuant to the Registration Statement or pursuant to an exemption from the
Securities Act; (iv) the Purchaser will not, directly or indirectly, offer, sell
(including sell short), pledge, transfer or otherwise dispose of (or solicit any
offers to buy, purchase or otherwise acquire or take a pledge of) any of the
Shares or Warrant Shares except in compliance with the Securities Act and the
rules and regulations promulgated thereunder; (v) the Purchaser has completed or
caused to be completed the Registration Statement Questionnaire and the Stock
Certificate and Warrant Questionnaire, both set forth on Appendix I attached
hereto, for use in preparation of the Registration Statement, and the answers
thereto are true, correct and complete in all material respects as of the date
hereof and will be true, correct and complete in all material respects as of the
effective date of the Registration Statement; (vi) the Purchaser has, in
connection with its decision to purchase the Units, relied solely upon the SEC
Documents and the representations and warranties contained herein, as well as
any investigation completed by the Purchaser or its counsel, accountants or
other investment advisers; and (vii) the Purchaser is an "accredited investor"
within the meaning of Rule 501 of Regulation D promulgated under the Securities
Act.

                  (c) Each Purchaser agrees not to make any sale of the Shares
or the Warrant Shares under the Registration Statement without effectively
causing the prospectus delivery requirement under the Securities Act to be
satisfied, and each Purchaser acknowledges and agrees that such Shares and
Warrant Shares are not transferable on the books of the Company unless the
certificate submitted to the transfer agent evidencing the Shares or the Warrant
Shares is accompanied by a separate officer's certificate: (i) in the form set
forth on Appendix II attached hereto, (ii) executed by an officer of, or other
authorized person designated by, the Purchaser, and (iii) to the effect that (A)
such Shares or Warrant Shares have been sold pursuant to and in accordance with
the Registration Statement and the "Plan of Distribution" section of the
prospectus included therein and (B) the requirement of delivering a current
prospectus has been




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satisfied, unless exempt from registration and prospectus delivery requirements.
Each Purchaser acknowledges that there may occasionally be times when the
Company must suspend the use of the prospectus forming a part of the
Registration Statement until such time as an amendment to the Registration
Statement has been filed by the Company and declared effective by the
Commission, or until such time as the Company has filed an appropriate report
with the Commission pursuant to the Exchange Act. Each Purchaser agrees that it
will not sell any Shares or Warrant Shares during the period commencing at the
time at which the Company gives the Purchaser notice of the suspension of the
use of said prospectus and ending at the time the Company gives the Purchaser
notice that the Purchaser may thereafter effect sales pursuant to said
prospectus. The Company shall only be able to suspend the use of said prospectus
for periods aggregating no more than one hundred twenty (120) days in any twelve
month period (the "Aggregate Period"), of which no individual period shall be
longer than sixty (60) consecutive days; provided, that should a Lock-Up Period
(as defined below in Section 5(e) hereof) occur, then the Aggregate Period for
the twelve month period during which such Lock-Up Period occurs shall be reduced
by a number of days equal to the number of days in such Lock-Up period, but in
no case shall the Aggregate Period be reduced to a number of days that is less
than sixty (60) days. Each Purchaser further agrees to notify promptly the
Company of the sale of any or all of such Purchaser's Shares or Warrant Shares,
and to notify promptly the Company in writing of any material changes in the
information set forth in the Registration Statement relating to such Purchaser
or its plan of distribution, or of any supplemental information required to be
included in the Registration Statement relating to its plan of distribution.

                  (d) Each Purchaser further represents and warrants, as of the
date hereof and as of the Closing Date, to, and covenants with, the Company
that: (i) the Purchaser has full right, power, authority and capacity to enter
into this Agreement and to consummate the transactions contemplated hereby and
has taken all necessary action to authorize the execution, delivery and
performance of this Agreement, and (ii) upon the execution and delivery of this
Agreement, this Agreement shall constitute a valid and binding obligation of the
Purchaser enforceable in accordance with its terms, except as may be limited by
applicable bankruptcy, insolvency, reorganization, moratorium or similar laws
affecting creditors' and contracting parties' rights generally and except as
enforceability may be subject to general principles of equity (regardless of
whether such enforceability is considered in a proceeding in equity or at law)
and except as the indemnification and contribution agreements of the Purchaser
in Section 7.4 hereof may be legally unenforceable.

                  (e) In consideration for the Company agreeing to its
obligations set forth in Section 7 below in respect of Shares and Warrant
Shares, each Purchaser agrees, in connection with any firm commitment
underwritten offering of the Common Stock, upon the request of the managing
underwriters of such offering, not to directly or indirectly (i) offer for sale,
sell, pledge, contract to sell or otherwise dispose of (or enter into any
transaction or device which is designed to, or could be expected to, result in
the disposition by any person at any time in the future of) any shares of Common
Stock or securities convertible into or exercisable or exchangeable for





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shares of Common Stock or (ii) enter into any swap or derivatives transaction
that transfers to another, in whole or in part, any of the economic benefits or
risks of ownership of shares of Common Stock, whether any such transaction
described in clause (i) or (ii) above is to be settled by delivery of shares of
Common Stock or other securities, in cash or otherwise, without the prior
written consent of such managing underwriters during the period of time
beginning ten days prior to the date when such managing underwriters advise the
Company that they expect to initiate such public offering and ending at a date
not to exceed ninety days from the commencement of such public offering (the
"Lock-Up Period"). Notwithstanding the foregoing, this obligation shall not
apply to the Purchaser unless each of the Company's directors and executive
officers who beneficially owns shares of Common Stock enters into a similar
agreement.

                  SECTION 6. Survival of Representations, Warranties and
Agreements. Notwithstanding any investigation made by any party to this
Agreement, all covenants, agreements, representations and warranties made by the
Company and the Purchaser herein shall survive the execution of this Agreement,
the delivery to the Purchaser of the Shares being purchased and the payment
therefor, for a period of one year following such payment therefor.


                  SECTION 7. Registration of Shares for Resale

                  7.1.     Registration Procedures and Expenses.

                  (a) The Company shall as soon as practicable after Closing,
but in no event later than twenty (20) days thereafter, prepare and file with
the Commission a registration statement on Form S-3 (or if such form is
unavailable to the Company, on such other form deemed appropriate for the
registration of the Common Stock by the Commission) (the "Registration
Statement") to register the Shares and Warrant Shares (collectively, the
"Registrable Shares") for resale by the Purchasers in non-underwritten, market
transactions, and shall use its best efforts to cause the Registration Statement
to become effective as soon as practicable thereafter. The Company shall, at
least three (3) business days before filing such Registration Statement, provide
a draft to each Purchaser and its counsel and its agent for review;

                  (b) The Company shall promptly prepare and file with the
Commission such amendments and supplements to the Registration Statement and the
prospectus used in connection therewith as may be necessary to keep such the
Registration Statement effective until such date when either all of the
Registrable Shares have been sold pursuant thereto or, by reason of Rule 144(k)
of the Commission under the Securities Act or any other rule of similar effect,
the Registrable Shares may be sold by the Purchasers in ordinary market
transactions without registration and without compliance with of any volume
limitations (the "Registration Period");

                  (c) The Company shall promptly furnish to each Purchaser and
its agent such number of copies of prospectuses and preliminary prospectuses in
conformity with the




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requirements of the Securities Act as such Purchaser or its agent may reasonably
request, in order to facilitate the public sale or other disposition of all or
any of the Shares by such Purchaser;

                  (d) The Company shall promptly file documents required of the
Company for any required blue sky clearance for the Registrable Shares in such
states specified in writing by each Purchaser or its agent; provided, however,
that the Company shall not be required to (i) qualify to do business or consent
to service of process in any jurisdiction in which it is not now so qualified or
has not so consented, (ii) subject itself to general taxation in any such
jurisdiction, (iii) provide any undertakings that cause the Company undue burden
or expense or (iv) make any change in its charter or bylaws;

                  (e) The Company shall promptly inform each Purchaser and its
agent when any stop order has been issued with respect to the Registration
Statement and use its commercially practical best efforts to promptly cause such
stop order to be withdrawn;

                  (f) The Company shall notify each Purchaser whose Registrable
Shares are registered on a Registration Statement and its agent at any time when
a prospectus relating to any Registrable Shares covered by such Registration
Statement or a Company Registration Statement is required to be delivered under
the Securities Act, of the happening of any event as a result of which the
prospectus included in such registration statement, as then in effect, includes
an untrue statement of a material fact or omits to state a material fact
required to be stated therein or necessary to make the statements therein not
misleading in light of the circumstances then existing and promptly file such
amendments and supplements as may be necessary so that, as thereafter delivered
to such Purchasers of such Registrable Shares, such prospectus shall not include
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
in light of the circumstances then existing and use its best commercially
practical efforts to cause each such amendment and supplement to become
effective;

                  (g) The Company shall bear all expenses in connection with the
procedures in clauses (a) through (f) in this Section 7.1 and the registration
of the Registrable Shares pursuant to the Registration Statement, other than
fees and expenses, if any, of counsel or other advisers to the Purchaser or the
Other Purchasers and any expenses relating to the sale of the Registrable Shares
by the Purchasers (including without limitation, broker's commissions, discounts
or fees of any nature and transfer taxes or charges of any nature); and

                  (h) The Company understands that each Purchaser disclaims
being an underwriter, but a Purchaser being deemed an underwriter shall not
relieve the Company of any obligations it has hereunder. A questionnaire related
to the Registration Statement to be completed by each Purchaser is set forth on
Appendix I.

                  7.2. Transfer of Registrable Shares. Each Purchaser agrees
that it will not effect any disposition of Registrable Shares except as
contemplated in the Registration Statement





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and as described in the "Plan of Distribution" section of the prospectus
included therein, or as otherwise in compliance with applicable securities laws,
and that it will promptly notify the Company of any material changes in the
information set forth in the Registration Statement regarding the Purchaser or
such "Plan of Distribution," Without limitation, each Purchaser understands that
(i) it may not use Registrable Shares to cover a short position in shares of the
Common Stock created prior to the effective date of the Registration Statement,
and (ii) it must deliver a prospectus in connection with any short sale of the
Registrable Shares unless it is exempt from such requirement.

                  7.3. Indemnification. For the purpose of this Section 7.3:

                  (a) the term "Selling Stockholder" shall include the
Purchaser, its officers, directors, agent and/or trustees and any affiliate or
controlling person of such Purchaser or any permitted assign hereunder;

                  (b) the term "Registration Statement" shall include any final
prospectus, exhibit, supplement or amendment included in or relating to the
Registration Statement referred to in Section 7.1; and

                  (c) the term "untrue statement" shall include any untrue
statement or alleged untrue statement, or any omission or alleged omission to
state in the Registration Statement a material fact required to be stated
therein or necessary to make the statements therein, in the light of the
circumstances under which they were made, not misleading.

                  The Company agrees to indemnify and hold harmless each Selling
Stockholder from and against any losses, claims, damages or liabilities to which
such Selling Stockholder may become subject (under the Securities Act or
otherwise) insofar as such losses, claims, damages or liabilities (or actions or
proceedings in respect thereof) arise out of, or are based upon, any breach of
the representations set forth in Section 4 hereof by the Company, or any untrue
statement of a material fact contained in the Registration Statement, or arise
out of any failure by the Company to fulfill any agreement, covenant or
undertaking contained in this Agreement or included in the Registration
Statement, and the Company will reimburse such Selling Stockholder for any
reasonable out-of-pocket legal or other documented out-of-pocket expenses
reasonably incurred in investigating, defending or preparing to defend any such
action, proceeding or claim; provided, however, that the Company shall not be
liable in any such case to the extent that such loss, claim, damage or liability
arises out of, or is based upon, (i) an untrue statement made in the
Registration Statement in reliance upon and in conformity with written
information furnished to the Company by or on behalf of such Selling Stockholder
specifically for use in the Registration Statement (which shall be deemed to
include the information set forth in the Registration Statement Questionnaire
and in the "Plan of Distribution" section of the prospectus included as part of
the Registration Statement), (ii) the failure of such Selling Stockholder to
comply with the covenants and agreements contained herein respecting transfer or
sale of Registrable Shares, or (iii) any statement or omission in any prospectus
that is corrected





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in any subsequent prospectus that was delivered to the Purchaser sufficiently
prior to the pertinent sale or sales by the Purchaser. The Company shall also
not be liable for amounts paid in settlement of any loss, claim, damage or
liability if such settlement if effected without the prior written consent of
the Company, which consent shall not be unreasonably withheld.

                  Each Purchaser agrees, severally and not jointly, to indemnify
and hold harmless the Company (and each person, if any, who controls the Company
within the meaning of Section 15 of the Securities Act, each officer of the
Company who signs the Registration Statement and each director of the Company)
from and against any losses, claims, damages or liabilities to which the Company
(or any such officer, director or controlling person) may become subject (under
the Securities Act or otherwise), insofar as such losses, claims, damages or
liabilities (or actions or proceedings in respect thereof) arise out of, or are
based upon, any breach of the representations set forth in Section 5 hereof by
such Purchaser, or any failure by such Purchaser to comply with the covenants
and agreements contained herein regarding the transfer or sale of Registrable
Shares, or any untrue statement of a material fact contained in the Registration
Statement if such untrue statement was made in reliance upon and in conformity
with written information furnished by or on behalf of the Purchaser specifically
for use in the Registration Statement. Each Purchaser will reimburse, severally
and not jointly, the Company (or such officer, director or controlling person),
as the case may be, for any out-of-pocket legal or other documented
out-of-pocket expenses reasonably incurred in investigating, defending or
preparing to defend any such action, proceeding or claim. Each Purchaser agrees
that the information regarding the Purchaser or its officers, directors and
affiliates and their intended plan of distribution of the Shares set forth in
the Registration Statement Questionnaire, the form of which is set forth on
Appendix I, or included from time to time in the Registration Statement
(including without limitation the "Plan of Distribution" section of the
prospectus included in the Registration Statement) shall be deemed to be written
information furnished to the Company by or on behalf of the Purchaser
specifically for use in the Registration Statement. The foregoing
indemnification shall be limited in amount as to each Purchaser to the Purchase
Price paid by such Purchaser hereunder.

                  Promptly after receipt by any indemnified person of a notice
of a claim or the beginning of any action in respect of which indemnity is to be
sought against an indemnifying person pursuant to this Section 7.3, such
indemnified person shall notify the indemnifying person in writing of such claim
or of the commencement of such action; provided, however, that any failure by an
indemnified person to notify an indemnifying person shall not relieve the
indemnifying person from its obligations hereunder except to the extent that the
indemnifying person is materially prejudiced thereby. Subject to the provisions
hereinafter stated, in case any such action shall be brought against an
indemnified person and such indemnifying person shall have been notified
thereof, such indemnifying person shall be entitled to participate therein, and,
to the extent it shall wish, to assume and control the defense thereof, with
counsel reasonably satisfactory to such indemnified person. After notice from
the indemnifying person to such indemnified person of its election to assume the
defense thereof, such indemnifying person shall not be liable to such
indemnified person for any legal expenses subsequently incurred by such






                                       11
<PAGE>   12

indemnified person in connection with the defense thereof; provided, however,
that if there exists a conflict of interest that would make it inappropriate, in
the opinion of counsel to the indemnifying person, for the same counsel to
represent both the indemnified person and such indemnifying person or any
affiliate or associate thereof, the indemnified person shall be entitled to
retain its own counsel at the expense of such indemnifying person; provided
further, however, that no indemnifying person shall be responsible for the fees
and expenses of more than one separate counsel for all indemnified parties
hereunder and under the other Agreements.

                  If the indemnification provided for in this Section 7.3 from
the indemnifying person would be applicable by its terms but is otherwise
unavailable, as determined by a court of applicable jurisdiction, to an
indemnified person hereunder in respect of any losses, claims, damages,
liabilities or expenses referred to herein, then the indemnifying person, in
lieu of indemnifying such indemnified person, shall contribute to the amount
paid or payable by such indemnified person as a result of such losses, claims,
damages, liabilities or expenses in such proportion as is appropriate to reflect
the relative fault of the indemnifying person and indemnified persons in
connection with the actions which resulted in such losses, claims, damages,
liabilities or expenses, as well as any other relevant equitable considerations.
The relative fault of such indemnifying person and indemnified persons shall be
determined by reference to, among other things, whether any action in question,
including any untrue or alleged untrue statement of a material fact, has been
made by, or relates to information supplied by, such indemnifying person or
indemnified persons, and the parties' relative intent, knowledge, access to
information and opportunity to correct or prevent such action. The amount paid
or payable by a party as a result of the losses, claims, damages, liabilities
and expenses referred to above shall be deemed to include, subject to the
limitations set forth in this Section 7.3, any reasonable legal or other fees or
expenses reasonably incurred by such party in connection with any investigation
or proceeding.

                  The parties hereto agree that it would not be just and
equitable if contribution pursuant to this Section 7.3 were determined by pro
rata allocation or by any other method of allocation which does not take account
of the equitable considerations referred to in the immediately preceding
paragraph. Notwithstanding the provisions of this Section 7.3, no Purchaser
shall be required to contribute any amount in excess of the aggregate dollar
amount of the proceeds received by such Purchaser upon the sale of the
Registrable Shares. 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.

                  7.4. Termination of Conditions and Obligations. The conditions
imposed by Section 5 or this Section 7 upon the transferability of Registrable
Shares shall cease and terminate as to any particular number of Registrable
Shares when the offering of such Registrable Shares shall have been effectively
registered under the Securities Act and sold or otherwise disposed of in
accordance with the intended method of disposition set forth in the Registration
Statement and the "Plan of Distribution" section of prospectus included therein,
or




                                       12
<PAGE>   13

at such time as an opinion of counsel satisfactory to the Company shall have
been rendered to the effect that such conditions are not necessary in order to
comply with the Securities Act.

                  7.5. Continued Availability of Information. So long as the
Registration Statement is effective covering the resale of Registrable Shares
owned by the Purchaser, the Company will furnish to the Purchaser:

                  (a) as soon as practicable after available (but in the case of
the Company's Annual Report to Stockholders, within 120 days after the end of
each fiscal year of the Company), one copy of (i) its Annual Report to
Stockholders (which Annual Report shall contain financial statements audited in
accordance with generally accepted accounting principles by a firm of certified
public accountants), (ii) if not included in substance in the Annual Report to
Stockholders, its Annual Report on Form 10-K, (iii) any quarterly reports to
stockholders, and if not included in substance in its quarterly reports to
stockholders, its quarterly reports on Form 10-Q, and (iv) a full copy of the
Registration Statement (the foregoing, in each case, excluding exhibits);

                  (b) upon the reasonable request of a Purchaser or its agent,
all exhibits excluded by the parenthetical to clause (a)(iv) of this Section 7.5
and all other information that is made available to stockholders; and

                  (c) upon the reasonable request of a Purchaser or its agent,
an adequate number of copies of the prospectuses to supply to any other party
requiring such prospectuses;

and the Company, upon the reasonable request of a Purchaser or its agent, will
meet with the Purchaser or a representative thereof at the Company's
headquarters to discuss all information relevant for disclosure in the
Registration Statement and will otherwise cooperate with any Purchaser
conducting an investigation for the purpose of reducing or eliminating such
Purchaser's exposure to liability under the Securities Act, including the
reasonable production at the Company's headquarters of non-confidential
information (and, upon execution of a confidentiality agreement satisfactory to
the Company, confidential information).

                  7.6. Reports under Exchange Act. With a view to making
available to the Purchasers the benefits of Rule 144 promulgated under the
Securities Act and any other rule or regulation of the Commission that may at
any time permit a Purchaser to sell Registrable Shares to the public without
registration, and with a view to making it possible to register the Registrable
Shares pursuant to a registration statement on Form S-3, the Company agrees to:

                  (a) make and keep available public information, as understood
and defined in Rule 144, at all times;

                  (b) file with the Commission in a timely manner all reports
and other documents required of the Company under the Securities Act and the
Exchange Act; and




                                       13
<PAGE>   14

                  (c) furnish to a Purchaser owning any Registrable Shares or
its agent upon reasonable request (i) a written statement by the Company that is
has complied with the reporting requirements of Rule 144, the Securities Act and
the Exchange Act, or that it qualifies as a registrant whose Registrable Shares
may be resold pursuant to a registration statement on Form S-3 (at any time
after it so qualified), (ii) a copy of the most recent annual or quarterly
report of the Company and such other reports and documents so filed by the
Company, and (iii) such other information as may be reasonably required in
availing any Purchaser of Registrable Shares of any rule or regulation of the
Commission which permits the selling of any such Registrable Shares without
registration or pursuant to such form.

                  SECTION 8. Broker's Fees. Each of the parties hereto hereby
represents that, on the basis of any actions and agreements by it, there are no
brokers or finders entitled to compensation in connection with the sale of the
Shares to the Purchasers, except for the Company's obligations as set forth on
Schedule A.

                  SECTION 9. Expenses. At the Closing, each party hereto shall
bear its own expenses.

                  SECTION 10. Notices. All notices, requests, consents and other
communications hereunder shall be in writing, shall be sent by a nationally
recognized overnight express courier postage prepaid, and shall be deemed given
one day after being so sent and shall be delivered as addressed as follows:

                  (a)      if to the Company, to:

                           Cell Pathways, Inc.
                           702 Electronic Drive
                           Horsham, PA 19044
                           Attention: Robert J. Towarnicki
                           President and Chief Executive Officer



                                       14
<PAGE>   15



                           with copies so mailed to:

                           Martha E. Manning, Esq.
                           Senior Vice President, General Counsel and Secretary
                           Cell Pathways, Inc.
                           702 Electronic Drive
                           Horsham, PA 19044

                           and to

                           Morgan, Lewis & Bockius LLP
                           1701 Market Street
                           Philadelphia, Pennsylvania  19103-2921
                           Attention:  Stephen Jannetta

                           or to such other person at such other place as the
                           Company shall designate to the Purchaser in
                           writing; and

                  (b) if to the Purchaser, at the address set forth on Schedule
A or Schedule B hereto, or at such other address or addresses as may have been
furnished to the Company in writing,

                  SECTION 11. Entire Agreement; Changes. This Agreement sets
forth the entire agreement of the parties and may not be modified or amended
except pursuant to an instrument in writing signed by the Company and the
Purchaser.

                  SECTION 12. Headings. The headings of the various sections of
this Agreement have been inserted for convenience of reference only and shall
not be deemed to be part of this Agreement.

                  SECTION 13. Severability. In case any provision contained in
this Agreement should be invalid, illegal or unenforceable in any respect, the
validity, legality and enforceability of the remaining provisions contained
herein shall not in any way be affected or impaired thereby.

                  SECTION 14. Governing Law. THIS AGREEMENT SHALL BE GOVERNED BY
AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF DELAWARE WITHOUT
GIVING EFFECT TO CONFLICTS OF LAWS.

                  SECTION 15. Counterparts. This Agreement may be executed in
two or more counterparts, each of which shall constitute an original, but all of
which, when taken together, shall constitute but one instrument, and shall
become effective when one or more counterparts have been signed by each party
hereto and delivered to the other parties.



                                       15
<PAGE>   16



                  IN WITNESS WHEREOF, the parties hereto have caused this
Agreement to be executed by their duly authorized representatives as of the day
and year first above written.


                                 CELL PATHWAYS, INC.


                                 By: /s/ Robert J. Towarnicki
                                    -----------------------------------------
                                     Robert J. Towarnicki
                                     President and Chief Executive Officer


                                 VULCAN VENTURES INC.


                                 By: /s/ William D. Savoy
                                    -----------------------------------------
                                     Name:   William D. Savoy
                                     Title:  President





                                       16
<PAGE>   17





                                   SCHEDULE A

                               [NAME OF PURCHASER]

NAME AND ADDRESS               NUMBER OF SHARES      PRICE          AGGREGATE
OF PURCHASERS                  TO BE PURCHASED     PER SHARE     PURCHASE PRICE

Vulcan Ventures Inc.               500,000          $7.375        $3,687,500.00

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

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

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


<PAGE>   18




                                                                      Appendix I
                                                                    (one of two)


                               CELL PATHWAYS, INC.
                   STOCK CERTIFICATE AND WARRANT QUESTIONNAIRE



Please provide us with the following information:

1.   The exact name that your Shares and Warrants
     (both must be in the same name) are to be
     registered. This is the name that will
     appear on your stock certificate(s) and
     Warrant(s). You may use a nominee name
     if appropriate:
                                                        ----------------------


2.   The relationship between the Purchaser of
     the Units and the registered holder listed
     in response to item 1 above:
                                                        ----------------------


3.   The mailing address of the registered holder
     listed in response to item 1 above:
                                                        ----------------------


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

4.   The social security number or tax identification
     number of the registered holder listed in
     response to item 1 above:
                                                        ----------------------


<PAGE>   19



                                                                     Appendix I
                                                                   (two of two)

                               CELL PATHWAYS, INC.
                      REGISTRATION STATEMENT QUESTIONNAIRE


                  In connection with the preparation of the Registration
Statement, please provide us with the following information:

                  1. Pursuant to the "Selling Stockholder" section of the
Registration Statement, please state your or your organization's name exactly as
it should appear in the Registration Statement:

                  2. Please provide the number of shares of Common Stock that
you or your organization will own beneficially or of record immediately after
Closing, including those Shares purchased by you or your organization pursuant
to this Purchase Agreement and those shares purchased by you or your
organization through other transactions (indicating whether you have sole or
shared voting or dispositive power over such securities as determined under
applicable rules of the Securities and Exchange Commission):

<TABLE>
<CAPTION>
        VOTING POWER                       DISPOSITIVE POWER
   Sole               Shared             Sole            Shared
<S>                <C>               <C>              <C>               <C>
                                                                         Common Stock beneficially owned prior to the
----------          ----------        ----------       ----------        date hereof

                                                                         Shares being purchased from the Company
----------          ----------        ----------       ----------

                                                                         Warrant Shares, issuable upon exercise of the Warrants
----------          ----------        ----------       ----------        being purchased from the Company

                                                                         Common Stock issuable upon exercise of other options or
----------          ----------        ----------       ----------        warrants that you may own, to the extent such shares of
                                                                         Common Stock are deemed to be beneficially owned

      TOTAL:                         shares of Common Stock beneficially owned
                     ---------------
</TABLE>


                  3. Have you or your organization had any position, office or
other material relationship within the past three years with the Company or its
affiliates other than as disclosed in the Company's proxy statement for its 2000
annual meeting of stockholders, or with Janney Montgomery Scott?




<PAGE>   20

                     _____ Yes         _____ No

            If yes, please indicate the nature of any such relationships below:

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

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

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

            4. Attached is a draft of the proposed "Plan of Distribution"
section of the prospectus included in the Registration Statement. Please confirm
that the draft is a correct and complete statement of your intended plan of
distribution.

                     _____ Yes         _____ No

<PAGE>   21




                              PLAN OF DISTRIBUTION

                  The Shares being offered by the Selling Stockholder or its
respective pledgees, donees, transferees or other successors in interest, will
be sold in one or more transactions (which may involve block transactions) on
the Nasdaq National Market or on such other market on which the Common Stock may
from time to time be trading, in privately negotiated transactions, through the
writing of options on the Shares, short sales or any combination thereof. The
sale price to the public may be the market price prevailing at the time of sale,
a price related to such prevailing market price or such other price as the
Selling Stockholder determines from time to time. The Shares may also be sold
pursuant to Rule 144. The Selling Stockholder shall have the sole and absolute
discretion not to accept any purchase offer or make any sale of Shares if they
deem the purchase price to be unsatisfactory at any particular time.

                  The Selling Stockholder or its respective pledgees, donees,
transferee or other successors in interest, may also sell the Shares directly to
market makers acting as principals and/or broker-dealers acting as agents for
themselves or their customers. Brokers acting as agents for the Selling
Stockholder will receive usual and customary commissions for brokerage
transactions, and market makers and block purchasers purchasing the Shares will
do so for their own account and at their own risk. It is possible that the
Selling Stockholder will attempt to sell shares of Common Stock in block
transactions to market makers or other purchasers at a price per share which may
be below the then market price. There can be no assurance with all or any of the
Shares offered hereby will be issued to, or sold by, the Selling Stockholder.
The Selling Stockholder and any brokers, dealers or agents, upon effecting the
sale of any of the Shares offered hereby, may be deemed "underwriters" as that
term is defined under the Securities Act or the Exchange Act, or the rules and
regulations thereunder.

                  The Selling Stockholder, alternatively, may sell all or any
part of the Shares offered hereby through an underwriter. The Selling
Stockholder has not entered into any agreement with a prospective underwriter
and there is no assurance that any such agreement will be entered into. If the
Selling Stockholder enters into such an agreement or agreements, the relevant
details will be set forth in a supplement or revisions to this prospectus.

                  Upon the Company being notified by the Selling Stockholder
that any material arrangement has been entered into with a broker or dealer for
the sale of Shares through a block trade, special offering, exchange
distribution or secondary distribution or a purchase by a broker or dealer, a
supplemented prospectus will be filed, if required, pursuant to Rule 424(c)
under the Securities Act, disclosing (a) the name of each such broker-dealer,
(b) the number of Shares involved, (c) the price at which such Shares were sold,
(d) the commissions paid or discounts or concessions allowed to such
broker-dealer(s), where applicable, (e) that such broker-dealer(s) did not
conduct any investigation to verify the information set out or incorporated by
reference in this prospectus, as supplemented, and (f) other facts material to
the transaction.



<PAGE>   22

                  The Selling Stockholder and any other persons participating in
the sale or distribution of the Shares will be subject to applicable provisions
of the Exchange Act and the rules and regulations thereunder, which provisions
may limit the timing of purchases and sales of any of the Shares by the Selling
Stockholder or any other such person. The foregoing may affect the marketability
of the Shares.

                   The Company has agreed to indemnify the Selling Stockholder,
or its transferees or assignees, against certain liabilities, including
liabilities under the Securities Act, or to contribute to payments the Selling
Stockholder or its respective pledgees, donees, transferees or other successors
in interest, may be required to make in respect thereof.

                  The Company is bearing all costs relating to the registration
of the Shares (other than fees and expenses, if any, of counsel or other
advisers to the Selling Stockholder). Any commissions, discounts or other fees
payable to broker-dealers in connection with any sale of the Shares will be
borne by the Selling Stockholder.





<PAGE>   23



                                                                    APPENDIX II

Attention:

                   PURCHASER'S CERTIFICATE OF SUBSEQUENT SALE

           The undersigned, [AN OFFICER OF, OR OTHER PERSON DULY AUTHORIZED BY]
___________________________________________________ [FILL IN OFFICIAL NAME OF
INDIVIDUAL OR INSTITUTION] hereby certifies that he/she [said institution] is
the Purchaser of the shares evidenced by the attached certificate, and as such,
sold such shares on ______________ [DATE] pursuant to and in accordance with
registration statement number ____________________ [FILL IN THE NUMBER OF OR
OTHERWISE IDENTIFY REGISTRATION STATEMENT] and the requirement of delivering a
current prospectus by the Company has been complied with in connection with such
sale.

Print or Type:

          Name of Purchaser
            (individual or
            institution):        ______________________

          Name of individual
            representing
            Purchaser (if an
            institution)         ______________________

          Title of individual
            representing
            Purchaser (if an
            institution):        ______________________

Signature by:

          Individual purchaser
            or individual repre-
            senting purchaser:   ______________________