<PAGE>   1

AS FILED  WITH THE  SECURITIES  AND  EXCHANGE  COMMISSION  ON  NOVEMBER  3, 1998

                                                      REGISTRATION NO. ---------


                    SECURITIES AND EXCHANGE COMMISSION
                          Washington, D.C. 20549



                                 FORM S-8
                          REGISTRATION STATEMENT
                                   UNDER
                        THE SECURITIES ACT OF 1933



                       CELL PATHWAYS HOLDINGS, INC.
          (Exact Name of Registrant as Specified in its Charter)



             DELAWARE                                     23-246900
     (State of Incorporation)                   (I.R.S. Employer Identification
                                                             No.)



                           702 ELECTRONIC DRIVE
                             HORSHAM, PA 19044

                 (Address of Principal Executive Offices)


              CELL PATHWAYS, INC. 1997 EQUITY INCENTIVE PLAN
    CELL PATHWAYS, INC. 1997 NON-EMPLOYEE DIRECTORS' STOCK OPTION PLAN
             CELL PATHWAYS, INC. EMPLOYEE STOCK PURCHASE PLAN
                  TSENG LABS, INC. 1991 STOCK OPTION PLAN
         TSENG LABS, INC. 1991 SPECIAL DIRECTORS STOCK OPTION PLAN
                  TSENG LABS, INC. 1995 STOCK OPTION PLAN

                         (Full Title of the Plan)


                           ROBERT J. TOWARNICKI
                          CHIEF EXECUTIVE OFFICER
                       CELL PATHWAYS HOLDINGS, INC.
                           702 ELECTRONIC DRIVE
                             HORSHAM, PA 19044
                              (215) 706-3800

  (Name, Address and Telephone Number, Including Area Code, of Agent for
                                 Service)
<PAGE>   2
                                COPIES TO:
                            REX R. O'NEAL, ESQ.
                            COOLEY GODWARD LLP
                     2595 CANYON BOULEVARD, SUITE 250
                       BOULDER, COLORADO 80302-6737
                              (303) 546-4000











<PAGE>   3
                         CALCULATION OF REGISTRATION FEE

<TABLE>
<CAPTION>
                                                                        PROPOSED
                                                  PROPOSED              MAXIMUM
TITLE OF SECURITIES        AMOUNT TO BE       MAXIMUM OFFERING          AGGREGATE       AMOUNT OF
TO BE REGISTERED          REGISTERED (1)     PRICE PER SHARE (1)       OFFERING PRICE   REGISTRATION FEE
--------------------------------------------------------------------------------------------------------
<S>                       <C>                <C>                      <C>               <C>      
Common Stock                1,777,214              $ 5.67
(par value $0.01)
                            1,574,286              $11.36              $27,968,499.36     $7,775.25
--------------------------------------------------------------------------------------------------------
</TABLE>


(1)      All share numbers and exercise prices assume: the assumption by
Registrant of the Cell Pathways, Inc. 1997 Equity Incentive Plan ("1997 Equity
Incentive Plan"), Cell Pathways, Inc. 1997 Non-Employee Directors' Stock Option
Plan ("1997 Non-Employee Directors' Plan"), Cell Pathways, Inc. Employee Stock
Purchase Plan ("Employee Stock Purchase Plan"), Tseng Labs, Inc. 1991 Stock
Option Plan ("Tseng 1991 Plan"), Tseng Labs, Inc. 1995 Stock Option Plan ("Tseng
1995 Plan") and Tseng Labs, Inc. 1991 Special Directors Stock Option Plan
("Tseng 1991 Special Directors Plan") (collectively, the "Plans"), and the
effectiveness of the conversion of the shares of Tseng Labs, Inc. and Cell
Pathways, Inc. into the right to be issued a number of shares of Registrant
using the Cell Pathways, Inc. conversion ratio and the Tseng Exchange Ratio
(incorporated by reference to the Registrant's Registration Statement on Form
S-4 (Registration No. 333-59557)).

         Estimated solely for the purpose of calculating the amount of the
registration fee pursuant to Rules 457(c) and 457(h)(1). The price per share and
aggregate offering price for shares subject to options previously granted and
currently outstanding under the Registrant's Plans are based upon the weighted
average exercise price pursuant to Rule 457(h)(1) under the Securities Act of
1933, as amended (the "Securities Act"). The price per share and aggregate
offering price for shares issuable upon exercise of options available for grant
under the Plans are based upon the closing price of Tseng Labs, Inc. Common
Stock as of the most recent practicable date, converted into an implied closing
price of Registrant using the Tseng Exchange Ratio (incorporated by reference to
the Registrant's Registration Statement on Form S-4 (Registration No.
333-59557)).

<TABLE>
<CAPTION>
------------------------------------------------------------------------------------------
   TYPE OF SHARES        NUMBER OF SHARES (2)    OFFERING PRICE PER  AGGREGATE OFFERING PRICE
                                                    SHARE(2)              
------------------------------------------------------------------------------------------
<S>                     <C>                       <C>                <C>          
Shares issuable             1,264,749                 $4.69           $5,937,466.40
pursuant to options
outstanding under
the 1997 Equity
Incentive Plan, the
1997 Non-Employee
Directors' Plan and
the Employee Stock
Purchase Plan
------------------------------------------------------------------------------------------
</TABLE>
<PAGE>   4
<TABLE>

<S>                     <C>                  <C>               <C>          
Shares issuable             512,465           $ 8.09           $4,147,144.00
pursuant to options
outstanding under
the Tseng 1995
Plan, the Tseng
1991 Plan and the
Tseng 1991 Special
Directors Plan
------------------------------------------------------------------------------------------
<S>                     <C>                  <C>               <C>          
Shares issuable           1,574,286            $11.36          $17,883,888.96
upon exercise of
options available
for grant under the
1997 Equity
Incentive Plan, the
1997 Non-Employee
Directors' Plan and
the Employee Stock
Purchase Plan
------------------------------------------------------------------------------------------
</TABLE>

(2)      All share numbers and exercise prices assume: the assumption by
Registrant of the Cell Pathways, Inc. 1997 Equity Incentive Plan ("1997 Equity
Incentive Plan"), Cell Pathways, Inc. 1997 Non-Employee Directors' Stock Option
Plan ("1997 Non-Employee Directors' Plan"), Cell Pathways, Inc. Employee Stock
Purchase Plan ("Employee Stock Purchase Plan"), Tseng Labs, Inc. 1991 Stock
Option Plan ("Tseng 1991 Plan"), Tseng Labs, Inc. 1995 Stock Option Plan ("Tseng
1995 Plan") and Tseng Labs, Inc. 1991 Special Directors Stock Option Plan
("Tseng 1991 Special Directors Plan") (collectively, the "Plans"), and the
effectiveness of the conversion of the shares of Tseng Labs, Inc. and Cell
Pathways, Inc. into the right to be issued a number of shares of Registrant
using the Cell Pathways, Inc. conversion ratio and the Tseng Exchange Ratio
(incorporated by reference to the Registrant's Registration Statement on Form
S-4 (Registration No. 333-59557)).

         Estimated solely for the purpose of calculating the amount of the
registration fee pursuant to Rules 457(c) and 457(h)(1). The price per share and
aggregate offering price for shares subject to options previously granted and
currently outstanding under the Registrant's Plans are based upon the weighted
average exercise price pursuant to Rule 457(h)(1) under the Securities Act of
1933, as amended (the "Securities Act"). The price per share and aggregate
offering price for shares issuable upon exercise of options available for grant
under the Plans are based upon the closing price of Tseng Labs, Inc. Common
Stock as of the most recent practicable date, converted into an implied closing
price of Registrant using the Tseng Exchange Ratio (incorporated by reference to
the Registrant's Registration Statement on Form S-4 (Registration No.
333-59557)).

<PAGE>   5
                 INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE

         The following documents filed by Cell Pathways Holdings, Inc. (the
"Registrant") with the Securities and Exchange Commission are incorporated by
reference into this Registration Statement:

         (a) The Registrant's Joint Proxy Statement/Prospectus dated September
21, 1998 (Registration No. 333-59557).

         (b) The description of the Registrant's Common Stock contained in the
Registrant's Registration Statement on Form S-4.

         (c) All reports and other documents hereafter filed by the Registrant
pursuant to Sections 13(a), 13(c), 14 and 15(d) of the Securities Exchange Act
of 1934, as amended (the "Exchange Act"), prior to the filing of a
post-effective amendment which indicates that all of the securities offered
hereby have been sold or which deregisters all such securities then remaining
unsold.

         Any statement contained in a document incorporated, or deemed to be
incorporated, by reference herein or contained in this Registration Statement
shall be deemed to be modified or superseded for purposes of this Registration
Statement to the extent that a statement contained herein or in any other
subsequently filed document which also is, or is deemed to be, incorporated by
reference herein modifies or supersedes such statement. Any such statement so
modified or superseded shall not be deemed, except as so modified or superseded,
to constitute a part of this Registration Statement.

                            DESCRIPTION OF SECURITIES

         Not applicable.

                     INTERESTS OF NAMED EXPERTS AND COUNSEL

         Not applicable.

                    INDEMNIFICATION OF DIRECTORS AND OFFICERS

         Under Section 145 of the Delaware General Corporation Law, the
Registrant has broad powers to indemnify its directors and officers against
liabilities they may incur in such capacities, including liabilities under the
Securities Act.

         The Registrant's Certificate of Incorporation provides for the
elimination of liability for monetary damages for breach of the directors'
fiduciary duty of care to the Registrant and its stockholders. These provisions
do not eliminate the directors' duty of care and, in appropriate circumstances,
equitable remedies such as injunctive or other forms of non-monetary relief will
remain available under Delaware law. In addition, each director will continue to
be subject to liability for breach of the director's duty of loyalty to the
Registrant, for acts or omissions not in good faith or involving intentional
misconduct, for knowing violations of law, for any transaction from which the
director derived an improper personal benefit, and for payment of dividends or
approval of stock repurchases or redemptions that are unlawful under Delaware
law. The provision does not affect a director's responsibilities under any other
laws, such as the federal securities laws or state or federal environmental
laws.

         The Registrant has entered into indemnification agreements with each of
its directors and executive officers under which the Registrant has agreed to
indemnify each of them against expenses and losses incurred for claims brought
against them by reason of their being a director or executive officer of the
Registrant and the Registrant maintains directors' and officers' liability
insurance.
<PAGE>   6
                       EXEMPTION FROM REGISTRATION CLAIMED

      Not applicable.

                                    EXHIBITS


      EXHIBIT
      NUMBER      DESCRIPTION

         4.1      Certificate of Incorporation of the Registrant (incorporated
                  by reference to Exhibit 3.1 to the Registrant's Registration
                  Statement on Form S-4 (Registration No. 333-59557)).

         4.2      Bylaws of the Registrant (incorporated by reference to Exhibit
                  3.2 to the Registrant's Registration Statement on Form S-4
                  (Registration No. 333-59557)).

         4.3      Specimen stock certificate (incorporated by reference to
                  Exhibit 4.2 to the Registrant's Registration Statement on Form
                  S-4 (Registration No. 333-59557)).

         5.1      Opinion of Cooley Godward LLP.

         10.1     Cell Pathways, Inc. 1997 Equity Incentive Plan (incorporated
                  by reference to Exhibit 10.3 to the Registrant's Registration
                  Statement on Form S-4 (Registration No. 333-59557)).

         10.2     Cell Pathways, Inc. 1997 Non-Employee Director Stock Option
                  Plan (incorporated by reference to Exhibit 10.5 to the
                  Registrant's Registration Statement on Form S-4 (Registration
                  No. 333-59557)).

         10.3     Cell Pathways, Inc. Employee Stock Purchase Plan. (1)

         10.4     Tseng Labs, Inc. 1991 Stock Option Plan (incorporated by
                  reference to Exhibit 10.20 to the Registrant's Registration
                  Statement on Form S-4 (Registration No. 333-59557)).

         10.5     Tseng Labs, Inc. 1991 Special Directors Stock Option Plan
                  (incorporated by reference to Exhibit 10.21 to the
                  Registrant's Registration Statement on Form S-4 (Registration
                  No. 333-59557)).

         10.6     Tseng Labs, Inc. 1995 Stock Option Plan (incorporated by
                  reference to Exhibit 10.22 to the Registrant's Registration
                  Statement on Form S-4 (Registration No. 333-59557)).

         23.1     Consent of Cooley Godward LLP (incorporated by reference to
                  Exhibit 5.1).
<PAGE>   7
         23.2     Consent of Arthur Andersen LLP.

         23.3     Consent of Arthur Andersen LLP.

         24       Power of Attorney. Reference is made to the signature pages.

         (1)      Filed as an exhibit to Cell Pathways, Inc.'s Registration
                  Statement on Form S-1, filed October 9, 1997, file number
                  333-37557, or amendments thereto and incorporated by
                  reference.
<PAGE>   8
        UNDERTAKINGS

         The Registrant hereby undertakes:

         (1) To file, during any period in which offers or sales are being made,
a post-effective amendment to this Registration Statement:

                   (i) To include any prospectus required by Section 10(a)(3) of
the Securities Act;

                   (ii) To reflect in the prospectus any facts or events arising
after the effective date of the Registration Statement (or the most recent
post-effective amendment thereof) which, individually or in the aggregate,
represent a fundamental change in the information set forth in the Registration
Statement. Notwithstanding the foregoing, any increase or decrease in volume of
securities offered (if the total dollar value of securities offered would not
exceed that which was registered) and any deviation from the low or high end of
the estimated maximum offering range may be reflected in the form of prospectus
filed with the Securities and Exchange Commission pursuant to Rule 424(b) if, in
the aggregate, the changes in volume and price represent no more than 20 percent
change in the maximum aggregate offering price set forth in the "Calculation of
Registration Fee" table in the effective Registration Statement;

                   (iii) To include any material information with respect to the
plan of distribution not previously disclosed in the Registration Statement or
any material change to such information in the Registration Statement;

         (2) That, for the purpose of determining any liability under the
Securities Act, each such post-effective amendment shall be deemed to be a new
registration statement relating to the securities offered therein, and the
offering of such securities at that time shall be deemed to be the initial bona
fide offering thereof.

         (3) To remove from registration by means of a post-effective amendment
any of the securities being registered which remain unsold at the termination of
the offering.

         The Registrant hereby undertakes that, for purposes of determining any
liability under the Securities Act, each filing of the Registrant's annual
report pursuant to Section 13(a) or 15(d) of the Exchange Act (and, where
applicable, each filing of an employee benefit plan's annual report pursuant to
Section 15(d) of the Exchange Act) that is incorporated by reference in the
Registration Statement shall be deemed to be a new registration statement
relating to the securities offered therein, and the offering of such securities
at that time shall be deemed to be the initial bona fide offering thereof.

         Insofar as indemnification for liabilities arising under the Securities
Act may be permitted to directors, officers and controlling persons of the
Registrant, the Registrant has been advised that in the opinion of the
Securities and Exchange Commission such indemnification is against public policy
as expressed in the Securities Act and is, therefore, unenforceable. In the
event that a claim for indemnification against such liabilities (other than the
payment by the Registrant of expenses incurred or paid by a director, officer or
controlling person of the Registrant in the successful defense of any action,
suit or proceeding) is asserted by such director, officer or controlling person
in connection with the securities being registered, the Registrant will, unless
in the opinion of its counsel the matter has been settled by controlling
precedent, submit to a court of appropriate jurisdiction the question whether
such indemnification by it is against public policy as expressed in the
Securities Act and will be governed by the final adjudication of such issue.
<PAGE>   9
                                SIGNATURES

         Pursuant to the requirements of the Securities Act, the Registrant
certifies that it has reasonable grounds to believe that it meets all of the
requirements for filing on Form S-8 and has duly caused this Registration
Statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the City of Horsham, State of Pennsylvania, on the 2nd day of
November, 1998.

                                          CELL PATHWAYS HOLDINGS, INC.


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

                             POWER OF ATTORNEY

         KNOW ALL PERSONS BY THESE PRESENTS, that each person whose signature
appears below constitutes and appoints Robert J. Towarnicki and Richard H. Troy,
and each of them, as his true and lawful attorneys-in-fact and agents, with full
power of substitution and resubstitution, for him and in his name, place and
stead, in any and all capacities, to sign any and all amendments (including
post-effective amendments) to this Registration Statement, and to file the same,
with all exhibits thereto, and all documents in connection therewith, with the
Securities and Exchange Commission, granting unto said attorneys-in-fact and
agents full power and authority to do and perform each and every act and thing
requisite and necessary to be done in connection therewith, as fully to all
intents and purposes as he might or could do in person, hereby ratifying and
confirming all that said attorneys-in-fact and agents, or any of them, or their
or his substitutes or substitute, may lawfully do or cause to be done by virtue
hereof.

         Pursuant to the requirements of the Securities Act, this Registration
Statement has been signed by the following persons in the capacities and on the
dates indicated.
<TABLE>
<CAPTION>

          SIGNATURE                         TITLE                                    DATE
<S>                                  <C>                                        <C>    
   /s/ Robert J. Towarnicki          Chief Executive Officer and                 November 2, 1998
   -----------------------           Director (Principal Executive Officer)
    Robert J. Towarnicki       

   /s/ Brian J. Hayden               Vice President - Finance,                   November 2, 1998
   -----------------------           Chief Financial Officer,      
       Brian J. Hayden               Treasurer (Principal Financial
                                     and Accounting Officer)       
                               
   /s/ Richard H. Troy               Senior Vice President - Corporate           November 2, 1998
   ----------------------            Development, General Counsel,          
       Richard H. Troy               Secretary and Director 
                                
  
   /s/ William A. Boeger             Chairman of the Board of                    November 2, 1998
  -----------------------            Directors
      William A. Boeger       

   /s/ Thomas M. Gibson              Director                                    November 2, 1998
  ---------------------
       Thomas M. Gibson

                                     Director                                    November 2, 1998
  ------------------------------
     Judith A. Hemberger


   /s/ Roger J. Quy                  Director                                    November 2, 1998
  ---------------------
     Roger J. Quy
</TABLE>
<PAGE>   10
<TABLE>

<S>                                  <C>                                       <C>      
   /s/ Bruce R. Ross                 Director                                    November 2, 1998  
  ----------------------                                                                           
     Bruce R. Ross                                                                                 
                                                                                                   
  /s/ Peter G. Schiff                Director                                    November 2, 1998  
  ----------------------                                                                           
     Peter G. Schiff                                                                               
                                                                                                   
  /s/ Randall M. Toig, M.D.                                                                        
  -------------------------          Director                                    November 2, 1998  
     Randall M. Toig, M.D.           
</TABLE>
<PAGE>   11
                              EXHIBIT INDEX


      EXHIBIT
      NUMBER      DESCRIPTION

         4.1      Certificate of Incorporation of the Registrant (incorporated
                  by reference to Exhibit 3.1 to the Registrant's Registration
                  Statement on Form S-4 (Registration No. 333-59557)).

         4.2      Bylaws of the Registrant (incorporated by reference to Exhibit
                  3.2 to the Registrant's Registration Statement on Form S-4
                  (Registration No. 333-59557)).

         4.3      Specimen stock certificate (incorporated by reference to
                  Exhibit 4.2 to the Registrant's Registration Statement on Form
                  S-4 (Registration No. 333-59557)).

         5.1      Opinion of Cooley Godward LLP.

         10.1     1997 Equity Incentive Plan of Cell Pathways, Inc.
                  (incorporated by reference to Exhibit 10.3 to the Registrant's
                  Registration Statement on Form S-4 (Registration No.
                  333-59557)).

         10.2     1997 Non-Employee Director Stock Option Plan of Cell Pathways,
                  Inc. (incorporated by reference to Exhibit 10.5 to the
                  Registrant's Registration Statement on Form S-4 (Registration
                  No. 333-59557)).

         10.3     Employee Stock Purchase Plan of Cell Pathways, Inc. (1)
                  

         10.4     Tseng Labs, Inc. 1991 Stock Option Plan (incorporated by
                  reference to Exhibit 10.20 to the Registrant's Registration
                  Statement on Form S-4 (Registration No. 333-59557)).

         10.5     Tseng Labs, Inc. 1991 Special Directors Stock Option Plan
                  (incorporated by reference to Exhibit 10.21 to the
                  Registrant's Registration Statement on Form S-4 (Registration
                  No. 333-59557)).

         10.6     Tseng Labs, Inc. 1995 Stock Option Plan (incorporated by
                  reference to Exhibit 10.22 to the Registrant's Registration
                  Statement on Form S-4 (Registration No. 333-59557)).

         23.1     Consent of Cooley Godward LLP (incorporated by reference to
                  Exhibit 5).
<PAGE>   12
         23.2     Consent of Arthur Andersen LLP.

         23.3     Consent of Arthur Andersen LLP.

         24       Power of Attorney. Reference is made to the signature pages.

         (1)      Filed as an exhibit to Cell Pathways, Inc.'s Registration
                  Statement on Form S-1, filed October 9, 1997, file number
                  333-37557, or amendments thereto and incorporated by
                  reference.
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1

AS FILED  WITH THE  SECURITIES  AND  EXCHANGE  COMMISSION  ON  NOVEMBER  3, 1998

                                                      REGISTRATION NO. ---------

                    SECURITIES AND EXCHANGE COMMISSION
                          Washington, D.C. 20549

                                 FORM S-8
                          REGISTRATION STATEMENT
                                   UNDER
                        THE SECURITIES ACT OF 1933

                       CELL PATHWAYS HOLDINGS, INC.
          (Exact Name of Registrant as Specified in its Charter)

             DELAWARE                                     23-246900
     (State of Incorporation)                   (I.R.S. Employer Identification
                                                             No.)

                           702 ELECTRONIC DRIVE
                             HORSHAM, PA 19044

                 (Address of Principal Executive Offices)

              CELL PATHWAYS, INC. 1997 EQUITY INCENTIVE PLAN
    CELL PATHWAYS, INC. 1997 NON-EMPLOYEE DIRECTORS' STOCK OPTION PLAN
             CELL PATHWAYS, INC. EMPLOYEE STOCK PURCHASE PLAN
                  TSENG LABS, INC. 1991 STOCK OPTION PLAN
         TSENG LABS, INC. 1991 SPECIAL DIRECTORS STOCK OPTION PLAN
                  TSENG LABS, INC. 1995 STOCK OPTION PLAN

                         (Full Title of the Plan)

                           ROBERT J. TOWARNICKI
                          CHIEF EXECUTIVE OFFICER
                       CELL PATHWAYS HOLDINGS, INC.
                           702 ELECTRONIC DRIVE
                             HORSHAM, PA 19044
                              (215) 706-3800

  (Name, Address and Telephone Number, Including Area Code, of Agent for
                                 Service)
2
                                COPIES TO:
                            REX R. O'NEAL, ESQ.
                            COOLEY GODWARD LLP
                     2595 CANYON BOULEVARD, SUITE 250
                       BOULDER, COLORADO 80302-6737
                              (303) 546-4000
3
                         CALCULATION OF REGISTRATION FEE
PROPOSED
                                                  PROPOSED              MAXIMUM
TITLE OF SECURITIES        AMOUNT TO BE       MAXIMUM OFFERING          AGGREGATE       AMOUNT OF
TO BE REGISTERED          REGISTERED (1)     PRICE PER SHARE (1)       OFFERING PRICE   REGISTRATION FEE
--------------------------------------------------------------------------------------------------------
Common Stock                1,777,214              $ 5.67
(par value $0.01)
                            1,574,286              $11.36              $27,968,499.36     $7,775.25
--------------------------------------------------------------------------------------------------------
(1)      All share numbers and exercise prices assume: the assumption by
Registrant of the Cell Pathways, Inc. 1997 Equity Incentive Plan ("1997 Equity
Incentive Plan"), Cell Pathways, Inc. 1997 Non-Employee Directors' Stock Option
Plan ("1997 Non-Employee Directors' Plan"), Cell Pathways, Inc. Employee Stock
Purchase Plan ("Employee Stock Purchase Plan"), Tseng Labs, Inc. 1991 Stock
Option Plan ("Tseng 1991 Plan"), Tseng Labs, Inc. 1995 Stock Option Plan ("Tseng
1995 Plan") and Tseng Labs, Inc. 1991 Special Directors Stock Option Plan
("Tseng 1991 Special Directors Plan") (collectively, the "Plans"), and the
effectiveness of the conversion of the shares of Tseng Labs, Inc. and Cell
Pathways, Inc. into the right to be issued a number of shares of Registrant
using the Cell Pathways, Inc. conversion ratio and the Tseng Exchange Ratio
(incorporated by reference to the Registrant's Registration Statement on Form
S-4 (Registration No. 333-59557)).

         Estimated solely for the purpose of calculating the amount of the
registration fee pursuant to Rules 457(c) and 457(h)(1). The price per share and
aggregate offering price for shares subject to options previously granted and
currently outstanding under the Registrant's Plans are based upon the weighted
average exercise price pursuant to Rule 457(h)(1) under the Securities Act of
1933, as amended (the "Securities Act"). The price per share and aggregate
offering price for shares issuable upon exercise of options available for grant
under the Plans are based upon the closing price of Tseng Labs, Inc. Common
Stock as of the most recent practicable date, converted into an implied closing
price of Registrant using the Tseng Exchange Ratio (incorporated by reference to
the Registrant's Registration Statement on Form S-4 (Registration No.
333-59557)).
------------------------------------------------------------------------------------------
   TYPE OF SHARES        NUMBER OF SHARES (2)    OFFERING PRICE PER  AGGREGATE OFFERING PRICE
                                                    SHARE(2)              
------------------------------------------------------------------------------------------
Shares issuable             1,264,749                 $4.69           $5,937,466.40
pursuant to options
outstanding under
the 1997 Equity
Incentive Plan, the
1997 Non-Employee
Directors' Plan and
the Employee Stock
Purchase Plan
------------------------------------------------------------------------------------------
4
Shares issuable             512,465           $ 8.09           $4,147,144.00
pursuant to options
outstanding under
the Tseng 1995
Plan, the Tseng
1991 Plan and the
Tseng 1991 Special
Directors Plan
------------------------------------------------------------------------------------------
Shares issuable           1,574,286            $11.36          $17,883,888.96
upon exercise of
options available
for grant under the
1997 Equity
Incentive Plan, the
1997 Non-Employee
Directors' Plan and
the Employee Stock
Purchase Plan
------------------------------------------------------------------------------------------
(2)      All share numbers and exercise prices assume: the assumption by
Registrant of the Cell Pathways, Inc. 1997 Equity Incentive Plan ("1997 Equity
Incentive Plan"), Cell Pathways, Inc. 1997 Non-Employee Directors' Stock Option
Plan ("1997 Non-Employee Directors' Plan"), Cell Pathways, Inc. Employee Stock
Purchase Plan ("Employee Stock Purchase Plan"), Tseng Labs, Inc. 1991 Stock
Option Plan ("Tseng 1991 Plan"), Tseng Labs, Inc. 1995 Stock Option Plan ("Tseng
1995 Plan") and Tseng Labs, Inc. 1991 Special Directors Stock Option Plan
("Tseng 1991 Special Directors Plan") (collectively, the "Plans"), and the
effectiveness of the conversion of the shares of Tseng Labs, Inc. and Cell
Pathways, Inc. into the right to be issued a number of shares of Registrant
using the Cell Pathways, Inc. conversion ratio and the Tseng Exchange Ratio
(incorporated by reference to the Registrant's Registration Statement on Form
S-4 (Registration No. 333-59557)).

         Estimated solely for the purpose of calculating the amount of the
registration fee pursuant to Rules 457(c) and 457(h)(1). The price per share and
aggregate offering price for shares subject to options previously granted and
currently outstanding under the Registrant's Plans are based upon the weighted
average exercise price pursuant to Rule 457(h)(1) under the Securities Act of
1933, as amended (the "Securities Act"). The price per share and aggregate
offering price for shares issuable upon exercise of options available for grant
under the Plans are based upon the closing price of Tseng Labs, Inc. Common
Stock as of the most recent practicable date, converted into an implied closing
price of Registrant using the Tseng Exchange Ratio (incorporated by reference to
the Registrant's Registration Statement on Form S-4 (Registration No.
333-59557)).
5
                 INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE

         The following documents filed by Cell Pathways Holdings, Inc. (the
"Registrant") with the Securities and Exchange Commission are incorporated by
reference into this Registration Statement:

         (a) The Registrant's Joint Proxy Statement/Prospectus dated September
21, 1998 (Registration No. 333-59557).

         (b) The description of the Registrant's Common Stock contained in the
Registrant's Registration Statement on Form S-4.

         (c) All reports and other documents hereafter filed by the Registrant
pursuant to Sections 13(a), 13(c), 14 and 15(d) of the Securities Exchange Act
of 1934, as amended (the "Exchange Act"), prior to the filing of a
post-effective amendment which indicates that all of the securities offered
hereby have been sold or which deregisters all such securities then remaining
unsold.

         Any statement contained in a document incorporated, or deemed to be
incorporated, by reference herein or contained in this Registration Statement
shall be deemed to be modified or superseded for purposes of this Registration
Statement to the extent that a statement contained herein or in any other
subsequently filed document which also is, or is deemed to be, incorporated by
reference herein modifies or supersedes such statement. Any such statement so
modified or superseded shall not be deemed, except as so modified or superseded,
to constitute a part of this Registration Statement.

                            DESCRIPTION OF SECURITIES

         Not applicable.

                     INTERESTS OF NAMED EXPERTS AND COUNSEL

         Not applicable.

                    INDEMNIFICATION OF DIRECTORS AND OFFICERS

         Under Section 145 of the Delaware General Corporation Law, the
Registrant has broad powers to indemnify its directors and officers against
liabilities they may incur in such capacities, including liabilities under the
Securities Act.

         The Registrant's Certificate of Incorporation provides for the
elimination of liability for monetary damages for breach of the directors'
fiduciary duty of care to the Registrant and its stockholders. These provisions
do not eliminate the directors' duty of care and, in appropriate circumstances,
equitable remedies such as injunctive or other forms of non-monetary relief will
remain available under Delaware law. In addition, each director will continue to
be subject to liability for breach of the director's duty of loyalty to the
Registrant, for acts or omissions not in good faith or involving intentional
misconduct, for knowing violations of law, for any transaction from which the
director derived an improper personal benefit, and for payment of dividends or
approval of stock repurchases or redemptions that are unlawful under Delaware
law. The provision does not affect a director's responsibilities under any other
laws, such as the federal securities laws or state or federal environmental
laws.

         The Registrant has entered into indemnification agreements with each of
its directors and executive officers under which the Registrant has agreed to
indemnify each of them against expenses and losses incurred for claims brought
against them by reason of their being a director or executive officer of the
Registrant and the Registrant maintains directors' and officers' liability
insurance.
6
                       EXEMPTION FROM REGISTRATION CLAIMED

      Not applicable.

                                    EXHIBITS

      EXHIBIT
      NUMBER      DESCRIPTION

         4.1      Certificate of Incorporation of the Registrant (incorporated
                  by reference to Exhibit 3.1 to the Registrant's Registration
                  Statement on Form S-4 (Registration No. 333-59557)).

         4.2      Bylaws of the Registrant (incorporated by reference to Exhibit
                  3.2 to the Registrant's Registration Statement on Form S-4
                  (Registration No. 333-59557)).

         4.3      Specimen stock certificate (incorporated by reference to
                  Exhibit 4.2 to the Registrant's Registration Statement on Form
                  S-4 (Registration No. 333-59557)).

         5.1      Opinion of Cooley Godward LLP.

         10.1     Cell Pathways, Inc. 1997 Equity Incentive Plan (incorporated
                  by reference to Exhibit 10.3 to the Registrant's Registration
                  Statement on Form S-4 (Registration No. 333-59557)).

         10.2     Cell Pathways, Inc. 1997 Non-Employee Director Stock Option
                  Plan (incorporated by reference to Exhibit 10.5 to the
                  Registrant's Registration Statement on Form S-4 (Registration
                  No. 333-59557)).

         10.3     Cell Pathways, Inc. Employee Stock Purchase Plan. (1)

         10.4     Tseng Labs, Inc. 1991 Stock Option Plan (incorporated by
                  reference to Exhibit 10.20 to the Registrant's Registration
                  Statement on Form S-4 (Registration No. 333-59557)).

         10.5     Tseng Labs, Inc. 1991 Special Directors Stock Option Plan
                  (incorporated by reference to Exhibit 10.21 to the
                  Registrant's Registration Statement on Form S-4 (Registration
                  No. 333-59557)).

         10.6     Tseng Labs, Inc. 1995 Stock Option Plan (incorporated by
                  reference to Exhibit 10.22 to the Registrant's Registration
                  Statement on Form S-4 (Registration No. 333-59557)).

         23.1     Consent of Cooley Godward LLP (incorporated by reference to
                  Exhibit 5.1).
7
         23.2     Consent of Arthur Andersen LLP.

         23.3     Consent of Arthur Andersen LLP.

         24       Power of Attorney. Reference is made to the signature pages.

         (1)      Filed as an exhibit to Cell Pathways, Inc.'s Registration
                  Statement on Form S-1, filed October 9, 1997, file number
                  333-37557, or amendments thereto and incorporated by
                  reference.
8
        UNDERTAKINGS

         The Registrant hereby undertakes:

         (1) To file, during any period in which offers or sales are being made,
a post-effective amendment to this Registration Statement:

                   (i) To include any prospectus required by Section 10(a)(3) of
the Securities Act;

                   (ii) To reflect in the prospectus any facts or events arising
after the effective date of the Registration Statement (or the most recent
post-effective amendment thereof) which, individually or in the aggregate,
represent a fundamental change in the information set forth in the Registration
Statement. Notwithstanding the foregoing, any increase or decrease in volume of
securities offered (if the total dollar value of securities offered would not
exceed that which was registered) and any deviation from the low or high end of
the estimated maximum offering range may be reflected in the form of prospectus
filed with the Securities and Exchange Commission pursuant to Rule 424(b) if, in
the aggregate, the changes in volume and price represent no more than 20 percent
change in the maximum aggregate offering price set forth in the "Calculation of
Registration Fee" table in the effective Registration Statement;

                   (iii) To include any material information with respect to the
plan of distribution not previously disclosed in the Registration Statement or
any material change to such information in the Registration Statement;

         (2) That, for the purpose of determining any liability under the
Securities Act, each such post-effective amendment shall be deemed to be a new
registration statement relating to the securities offered therein, and the
offering of such securities at that time shall be deemed to be the initial bona
fide offering thereof.

         (3) To remove from registration by means of a post-effective amendment
any of the securities being registered which remain unsold at the termination of
the offering.

         The Registrant hereby undertakes that, for purposes of determining any
liability under the Securities Act, each filing of the Registrant's annual
report pursuant to Section 13(a) or 15(d) of the Exchange Act (and, where
applicable, each filing of an employee benefit plan's annual report pursuant to
Section 15(d) of the Exchange Act) that is incorporated by reference in the
Registration Statement shall be deemed to be a new registration statement
relating to the securities offered therein, and the offering of such securities
at that time shall be deemed to be the initial bona fide offering thereof.

         Insofar as indemnification for liabilities arising under the Securities
Act may be permitted to directors, officers and controlling persons of the
Registrant, the Registrant has been advised that in the opinion of the
Securities and Exchange Commission such indemnification is against public policy
as expressed in the Securities Act and is, therefore, unenforceable. In the
event that a claim for indemnification against such liabilities (other than the
payment by the Registrant of expenses incurred or paid by a director, officer or
controlling person of the Registrant in the successful defense of any action,
suit or proceeding) is asserted by such director, officer or controlling person
in connection with the securities being registered, the Registrant will, unless
in the opinion of its counsel the matter has been settled by controlling
precedent, submit to a court of appropriate jurisdiction the question whether
such indemnification by it is against public policy as expressed in the
Securities Act and will be governed by the final adjudication of such issue.
9
                                SIGNATURES

         Pursuant to the requirements of the Securities Act, the Registrant
certifies that it has reasonable grounds to believe that it meets all of the
requirements for filing on Form S-8 and has duly caused this Registration
Statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the City of Horsham, State of Pennsylvania, on the 2nd day of
November, 1998.

                                          CELL PATHWAYS HOLDINGS, INC.

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

                             POWER OF ATTORNEY

         KNOW ALL PERSONS BY THESE PRESENTS, that each person whose signature
appears below constitutes and appoints Robert J. Towarnicki and Richard H. Troy,
and each of them, as his true and lawful attorneys-in-fact and agents, with full
power of substitution and resubstitution, for him and in his name, place and
stead, in any and all capacities, to sign any and all amendments (including
post-effective amendments) to this Registration Statement, and to file the same,
with all exhibits thereto, and all documents in connection therewith, with the
Securities and Exchange Commission, granting unto said attorneys-in-fact and
agents full power and authority to do and perform each and every act and thing
requisite and necessary to be done in connection therewith, as fully to all
intents and purposes as he might or could do in person, hereby ratifying and
confirming all that said attorneys-in-fact and agents, or any of them, or their
or his substitutes or substitute, may lawfully do or cause to be done by virtue
hereof.

         Pursuant to the requirements of the Securities Act, this Registration
Statement has been signed by the following persons in the capacities and on the
dates indicated.
SIGNATURE                         TITLE                                    DATE
/s/ Robert J. Towarnicki          Chief Executive Officer and                 November 2, 1998
   -----------------------           Director (Principal Executive Officer)
    Robert J. Towarnicki       

   /s/ Brian J. Hayden               Vice President - Finance,                   November 2, 1998
   -----------------------           Chief Financial Officer,      
       Brian J. Hayden               Treasurer (Principal Financial
                                     and Accounting Officer)       
                               
   /s/ Richard H. Troy               Senior Vice President - Corporate           November 2, 1998
   ----------------------            Development, General Counsel,          
       Richard H. Troy               Secretary and Director 
                                
  
   /s/ William A. Boeger             Chairman of the Board of                    November 2, 1998
  -----------------------            Directors
      William A. Boeger       

   /s/ Thomas M. Gibson              Director                                    November 2, 1998
  ---------------------
       Thomas M. Gibson

                                     Director                                    November 2, 1998
  ------------------------------
     Judith A. Hemberger

   /s/ Roger J. Quy                  Director                                    November 2, 1998
  ---------------------
     Roger J. Quy
10
/s/ Bruce R. Ross                 Director                                    November 2, 1998  
  ----------------------                                                                           
     Bruce R. Ross                                                                                 
                                                                                                   
  /s/ Peter G. Schiff                Director                                    November 2, 1998  
  ----------------------                                                                           
     Peter G. Schiff                                                                               
                                                                                                   
  /s/ Randall M. Toig, M.D.                                                                        
  -------------------------          Director                                    November 2, 1998  
     Randall M. Toig, M.D.
11
                              EXHIBIT INDEX

      EXHIBIT
      NUMBER      DESCRIPTION

         4.1      Certificate of Incorporation of the Registrant (incorporated
                  by reference to Exhibit 3.1 to the Registrant's Registration
                  Statement on Form S-4 (Registration No. 333-59557)).

         4.2      Bylaws of the Registrant (incorporated by reference to Exhibit
                  3.2 to the Registrant's Registration Statement on Form S-4
                  (Registration No. 333-59557)).

         4.3      Specimen stock certificate (incorporated by reference to
                  Exhibit 4.2 to the Registrant's Registration Statement on Form
                  S-4 (Registration No. 333-59557)).

         5.1      Opinion of Cooley Godward LLP.

         10.1     1997 Equity Incentive Plan of Cell Pathways, Inc.
                  (incorporated by reference to Exhibit 10.3 to the Registrant's
                  Registration Statement on Form S-4 (Registration No.
                  333-59557)).

         10.2     1997 Non-Employee Director Stock Option Plan of Cell Pathways,
                  Inc. (incorporated by reference to Exhibit 10.5 to the
                  Registrant's Registration Statement on Form S-4 (Registration
                  No. 333-59557)).

         10.3     Employee Stock Purchase Plan of Cell Pathways, Inc. (1)
                  

         10.4     Tseng Labs, Inc. 1991 Stock Option Plan (incorporated by
                  reference to Exhibit 10.20 to the Registrant's Registration
                  Statement on Form S-4 (Registration No. 333-59557)).

         10.5     Tseng Labs, Inc. 1991 Special Directors Stock Option Plan
                  (incorporated by reference to Exhibit 10.21 to the
                  Registrant's Registration Statement on Form S-4 (Registration
                  No. 333-59557)).

         10.6     Tseng Labs, Inc. 1995 Stock Option Plan (incorporated by
                  reference to Exhibit 10.22 to the Registrant's Registration
                  Statement on Form S-4 (Registration No. 333-59557)).

         23.1     Consent of Cooley Godward LLP (incorporated by reference to
                  Exhibit 5).
12
         23.2     Consent of Arthur Andersen LLP.

         23.3     Consent of Arthur Andersen LLP.

         24       Power of Attorney. Reference is made to the signature pages.

         (1)      Filed as an exhibit to Cell Pathways, Inc.'s Registration
                  Statement on Form S-1, filed October 9, 1997, file number
                  333-37557, or amendments thereto and incorporated by
                  reference.