<PAGE>

                                                                     EXHIBIT 4.5

      FORM OF COMMON STOCK PURCHASE WARRANT - CRIPPLE CREEK SECURITIES, LLC

THESE SECURITIES HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, OR
ANY STATE SECURITIES LAWS. THEY MAY NOT BE SOLD OR OFFERED FOR SALE EXCEPT
PURSUANT TO AN EFFECTIVE REGISTRATION STATEMENT AS TO THE SECURITIES UNDER SAID
ACT AND ANY APPLICABLE STATE SECURITIES LAWS OR AN APPLICABLE EXEMPTION FROM
SUCH REGISTRATION REQUIREMENTS.

                                  CYGNUS, INC.

                          Common Stock Purchase Warrant

      Cygnus, Inc., a Delaware corporation (the "Company"), hereby certifies
that for good and valuable consideration, the receipt and sufficiency of which
are hereby acknowledged, Cripple Creek Securities, LLC, having an address at 195
Maplewood Avenue, Maplewood, New Jersey 07040, ("Purchaser") or any other
Warrant Holder (hereinafter defined) is entitled, on the terms and conditions
set forth below, to purchase from the Company at any time after the date hereof
(subject to the provisions of Section 2 hereof) and ending sixty (60) months
after the date hereof, up to that number of fully paid and nonassessable shares
of the common stock, par value $.001 per share, of the Company (the "Common
Stock") as determined pursuant to Section 2.6 of the Agreement (hereinafter
defined) at the Purchase Price (hereinafter defined) per share, as the same may
be adjusted pursuant to Section 5 herein.

1.   DEFINITIONS.

      (a) The term "Purchase Price" shall mean $___ per share.

      (b) The term "Warrant Holder" shall mean the Purchaser or any permitted
assignee of all or any portion of this Warrant, subject to the limitations set
forth herein.

      (c) The term "Warrant Shares" shall mean the shares of Common Stock or
other securities issuable upon exercise of this Warrant.

      (d) Other terms used herein which are defined in the Structured Equity
Line Flexible Financing(SM) Agreement by and between the Company and the
Purchaser, dated as of March 23, 2001 (the "Agreement") or the Registration
Rights Agreement by and between the Company and the Purchaser, dated as of June
30, 1999 (the "Rights Agreement"), shall have the same meanings herein as
therein.

2.   EXERCISE OF WARRANT.

      This Warrant may be exercised by Warrant Holder, in whole or in part, at
any time and from time to time, on or prior to the date sixty (60) months from
the date hereof, by either of the following methods:

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      (a) The Warrant Holder may surrender this Warrant, together with cash, a
certified check payable to the Company or wire transfer of immediately available
funds to an account designated by the Company representing the aggregate
Purchase Price of the number of Warrant Shares for which the Warrant is being
surrendered and the form of subscription attached hereto as EXHIBIT A, duly
executed by Warrant Holder ("Subscription Notice"), at the offices of the
Company; or

      (b) The Warrant Holder may also exercise this Warrant, in whole or in
part, on a "cashless" or "net-issue" basis by delivering to the offices of the
Company this Warrant, together with a Subscription Notice specifying the number
of Warrant Shares to be delivered to the Warrant Holder and the number of
Warrant Shares to be surrendered in payment of the aggregate Purchase Price
according to the following formula:

                          D = FMV - PP multiplied by SS
                              --------
                                 FMV

Where

"D" means the number of Warrant Shares to be delivered on exercise of the
Warrant,
"FMV" means the Fair Market Value, and
"SS" means the number of Warrant Shares to be delivered in payment of the
Purchase Price
"PP" means Purchase Price

      (c) such that, without the exchange of any funds, the Warrant Holder will
receive that number of Warrant Shares (and such other consideration otherwise
issuable, or payable, upon exercise of this Warrant) less that number of Warrant
Shares having an aggregate Fair Market Value on the date prior to the date of
exercise equal to the aggregate Purchase Price that would otherwise have been
paid by the Warrant Holder as specified in the Subscription Notice.

      In the event that the Warrant is not exercised in full, the number of
Warrant Shares shall be reduced by the number of such Warrant Shares for which
this Warrant is exercised, and the Company, at its expense, shall forthwith
issue and deliver or upon the order of Warrant Holder a new Warrant of like
tenor in the name of Warrant Holder or as Warrant Holder (upon payment by
Warrant Holder of any applicable transfer taxes) may request, reflecting such
adjusted Warrant Shares.

3.   DELIVERY OF CERTIFICATES.

      (a) Subject to the terms and conditions of this Warrant, as soon as
practicable after the exercise of this Warrant in full or in part, and in any
event within three (3) Trading Days thereafter, the Company shall transmit the
certificates (together with any other stock or other securities or property to
which Warrant Holder is entitled upon exercise) by messenger or overnight
delivery service to reach the address designated by such holder within three (3)
trading days after the receipt of the Warrant, the Subscription Notice and
payment of the aggregate Purchase Price in Section 2(a) or 2(b), as appropriate
("T+3"). In lieu of delivering physical certificates representing the Common
Stock issuable upon exercise, provided the Company's transfer agent is
participating in the Depository Trust Company ("DTC") Fast Automated Securities
Transfer ("FAST") program, upon request of the Warrant Holder, the Company shall

                                       2

<PAGE>

use its best efforts to cause its transfer agent to electronically transmit the
Common Stock issuable upon exercise to the Warrant Holder by crediting the
account of Warrant Holder's prime broker with DTC through its Deposit Withdrawal
Agent Commission ("DWAC") system. The time periods for delivery described in the
immediately preceding paragraph shall apply to the electronic transmittals
described herein.

      (b) This Warrant may not be exercised as to fractional shares of Common
Stock. In the event that the exercise of this Warrant, in full or in part, would
result in the issuance of any fractional share of Common Stock, then in such
event Warrant Holder shall be entitled to cash equal to the Fair Market Value of
such fractional share.

4.   REPRESENTATIONS AND COVENANTS.

      (a) REPRESENTATIONS AND COVENANTS OF THE COMPANY. From the date hereof
through the last date on which this Warrant is exercisable, the Company shall
take all steps reasonably necessary and within its control to insure that the
Common Stock remains listed on a Principal Market so long as it is publicly
traded and shall not amend its Certificate of Incorporation or Bylaws so as to
adversely affect any rights of the Warrant Holder under this Warrant in any
material respect.

      (b) REPRESENTATIONS AND COVENANTS OF THE PURCHASER. The Purchaser shall
not resell Warrant Shares, unless such resale is pursuant to an effective
registration statement under the Act or pursuant to an applicable exemption from
such registration requirements and such sale otherwise complies with state and
federal securities laws.

5.   ADJUSTMENT OF PURCHASE PRICE AND NUMBER OF SHARES.

      The number and kind of securities purchasable upon exercise of this
Warrant and the Purchase Price shall be subject to adjustment from time to time
as follows:

      (a) SUBDIVISIONS, COMBINATIONS AND OTHER ISSUANCES. If the Company shall
at any time after the date hereof but prior to the expiration of this Warrant
subdivide its outstanding securities as to which purchase rights under this
Warrant exist, by split-up, or otherwise, or combine its outstanding securities
as to which purchase rights under this Warrant exist, the number of Warrant
Shares as to which this Warrant is exercisable as of the date of such split-up
or combination shall forthwith be proportionately increased in the case of a
split-up, or proportionately decreased in the case of a combination. Appropriate
adjustments shall also be made to the Purchase Price payable per share, so that
the aggregate Purchase Price payable for the total number of Warrant Shares
purchasable under this Warrant as of such date shall remain the same.

      (b) STOCK DIVIDEND. If at any time after the date hereof but prior to the
expiration of this Warrant, the Company declares a dividend or other
distribution on Common Stock payable in Common Stock or other securities or
rights convertible into Common Stock ("Common Stock Equivalents") without
payment of any consideration by holders of Common Stock for the additional
shares of Common Stock or the Common Stock Equivalents (including the additional
shares of Common Stock issuable upon exercise or conversion thereof), then the
number of

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shares of Common Stock for which this Warrant may be exercised shall be
increased as of the record date (or the date of such dividend distribution if no
record date is set) for determining which holders of Common Stock shall be
entitled to receive such dividends, in proportion to the increase in the number
of outstanding shares (and shares of Common Stock issuable upon conversion of
all such securities convertible into Common Stock) of Common Stock as a result
of such dividend, and the Purchase Price per share shall be adjusted so that the
aggregate Purchase Price for the Warrant Shares issuable hereunder immediately
after the record date (or on the date of such distribution, if applicable), for
such dividend shall equal the aggregate Purchase Price immediately before such
record date (or on the date of such distribution, if applicable).

      (c) OTHER DISTRIBUTIONS. If at any time after the date hereof but prior to
the expiration of this Warrant, the Company distributes to holders of its Common
Stock, other than as part of its dissolution, liquidation or the winding up of
its affairs, any shares of its capital stock, any evidence of indebtedness or
any of its assets (other than cash, Common Stock or securities convertible into
or exchangeable for Common Stock), then the number of Warrant Shares for which
this Warrant is exercisable shall be increased to equal: (i) the number of
Warrant Shares for which this Warrant is exercisable immediately prior to such
event, (ii) multiplied by a fraction, (A) the numerator of which shall be the
Fair Market Value per share of Common Stock on the record date for the dividend
or distribution, and (B) the denominator of which shall be the Fair Market Value
per share of Common Stock on the record date for the dividend or distribution
minus the amount allocable to one share of Common Stock of the value (as
determined in good faith by the Board of Directors of the Company) of any and
all such evidences of indebtedness, shares of capital stock, other securities or
property, so distributed. The Purchase Price shall be reduced to equal: (i) the
Purchase Price in effect immediately before the occurrence of any such event
(ii) multiplied by a fraction, (A) the numerator of which is the number of
Warrant Shares for which this Warrant is exercisable immediately before the
adjustment, and (B) the denominator of which is the number of Warrant Shares for
which this Warrant is exercisable immediately after the adjustment.

      (d) MERGER, ETC. If at any time after the date hereof there shall be a
merger or consolidation of the Company with or into or a transfer of all or
substantially all of the assets of the Company to another entity, then the
Warrant Holder shall be entitled to receive upon payment of the aggregate
Purchase Price then in effect, the number of shares or other securities or
property of the Company or of the successor corporation resulting from such
merger or consolidation, which would have been received by Warrant Holder for
the shares of stock subject to this Warrant had this Warrant been exercised just
prior to such transfer, merger or consolidation becoming effective or to the
applicable record date thereof, as the case may be. The Company will not merge
into or consolidate with or into any other corporation, or sell or otherwise
transfer its property, assets and business substantially as an entirety to
another corporation, unless the corporation resulting from such merger or
consolidation (if not the Company), or such transferee corporation, as the case
may be, shall expressly assume, by supplemental agreement reasonably
satisfactory in form and substance to the Warrant Holder, the due and punctual
performance and observance of each and every covenant and condition of this
Warrant to be performed and observed by the Company.

                                       4

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      (e) RECLASSIFICATION, ETC. If at any time after the date hereof there
shall be a reorganization or reclassification of the securities as to which
purchase rights under this Warrant exist into the same or a different number of
securities of any other class or classes, then the Warrant Holder shall
thereafter be entitled to receive upon exercise of this Warrant, during the
period specified herein and upon payment of the Purchase Price then in effect,
the number of shares or other securities or property resulting from such
reorganization or reclassification, which would have been received by the
Warrant Holder for the shares of stock subject to this Warrant had this Warrant
at such time been exercised.

6.   NO IMPAIRMENT.

      The Company will not, by amendment of its Certificate of Incorporation or
through any reorganization, transfer of assets, consolidation, merger,
dissolution, issue or sale of securities or any other voluntary action, avoid or
seek to avoid the observance or performance of any of the terms of this Warrant,
but will at all times in good faith assist in the carrying out all of such terms
and in the taking of all such action as may be reasonably necessary or
appropriate in order to protect the rights of the Warrant Holder against
impairment. Without limiting the generality of the foregoing, the Company (a)
will not increase the par value of any Warrant Shares above the amount payable
therefor on such exercise, and (b) will take all such action as may be
reasonably necessary or appropriate in order that the Company may validly and
legally issue fully paid and nonassessable Warrant Shares on the exercise of
this Warrant.

7.   NOTICE OF ADJUSTMENTS.

      Whenever the Purchase Price or number of Warrant Shares purchasable
hereunder shall be adjusted pursuant to Section 5 hereof, the Company shall
execute and deliver to the Warrant Holder (by first class mail, postage prepaid)
a certificate setting forth, in reasonable detail, the event requiring the
adjustment, the amount of the adjustment, the method by which such adjustment
was calculated and the Purchase Price and number of shares purchasable hereunder
after giving effect to such adjustment.

8.   RIGHTS AS SHAREHOLDER.

      Prior to exercise of this Warrant, the Warrant Holder shall not be
entitled to any rights as a stockholder of the Company with respect to the
Warrant Shares, including (without limitation) the right to vote such shares,
receive dividends or other distributions thereon or be notified of stockholder
meetings. However, in the event of any taking by the Company of a record of the
holders of any class of securities for the purpose of determining the holders
thereof who are entitled to receive any dividend or other distribution (other
than a cash dividend), any right to subscribe for, purchase or otherwise acquire
any shares of stock of any class or any other securities or property, or to
receive any other right (other than the right to vote), the Company shall
provide notice pursuant to Section 13 below to each Warrant Holder, at least 10
days prior to the date of such record, therein, a notice specifying the date on
which any such record is to be taken for the purpose of such dividend,
distribution or right, and the amount and character of such dividend,
distribution or right.

                                       5

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9.   LIMITATION ON EXERCISE.

      Notwithstanding anything to the contrary contained herein, this Warrant
may not be exercised by the Warrant Holder to the extent that, after giving
effect to Warrant Shares to be issued pursuant to a Subscription Notice, the
total number of shares of Common Stock deemed beneficially owned by such holder
(other than by virtue of ownership of this Warrant, or ownership of other
securities that have limitations on the holder's rights to convert or exercise
similar to the limitations set forth herein), together with all shares of Common
Stock deemed beneficially owned by the holder's "affiliates" (as defined in Rule
144 of the Act) that would be aggregated for purposes of determining whether a
group under Section 13(d) of the Securities Exchange Act of 1934 exists, would
exceed 9.9% of the total issued and outstanding shares of the Common Stock. The
delivery of a Subscription Notice by the Warrant Holder shall be deemed a
representation by such holder that it is in compliance with this paragraph. The
term "deemed beneficially owned" as used in this Warrant shall exclude shares
that might otherwise be deemed beneficially owned by reason of the exercise of
this Warrant.

10.  REPLACEMENT OF WARRANT.

      On receipt of evidence reasonably satisfactory to the Company of the loss,
theft, destruction or mutilation of the Warrant and, in the case of any such
loss, theft or destruction of the Warrant, on delivery of an indemnity agreement
or security reasonably satisfactory in form and amount to the Company or, in the
case of any such mutilation, on surrender and cancellation of such Warrant, the
Company, at the Warrant Holder's expense will execute and deliver, in lieu
thereof, a new Warrant of like tenor.

11.  SPECIFIC ENFORCEMENT; CONSENT TO JURISDICTION AND CHOICE OF LAW.

      (a) The Company and the Warrant Holder acknowledge and agree that
irreparable damage would occur in the event that any of the provisions of this
Warrant were not performed in accordance with their specific terms or were
otherwise breached. It is accordingly agreed that the parties shall be entitled
to an injunction or injunctions to prevent or cure breaches of the provisions of
this Warrant and to enforce specifically the terms and provisions hereof, this
being in addition to any other remedy to which either of them may be entitled by
law or equity.

      (b) EACH OF THE COMPANY AND THE WARRANT HOLDER (I) HEREBY IRREVOCABLY
SUBMITS TO THE EXCLUSIVE JURISDICTION OF THE STATE AND FEDERAL COURT LOCATED IN
SAN FRANCISCO COUNTY, CALIFORNIA FOR THE PURPOSES OF ANY SUIT, ACTION OR
PROCEEDING ARISING OUT OF OR RELATING TO THIS WARRANT AND (II) HEREBY WAIVES,
AND AGREES NOT TO ASSERT IN ANY SUCH SUIT, ACTION OR PROCEEDING, ANY CLAIM THAT
IT IS NOT PERSONALLY SUBJECT TO THE JURISDICTION OF SUCH COURT, THAT THE SUIT,
ACTION OR PROCEEDING IS BROUGHT IN AN INCONVENIENT FORUM OR THAT THE VENUE OF
THE SUIT, ACTION OR PROCEEDING IS IMPROPER. EACH OF THE COMPANY AND THE WARRANT
HOLDER CONSENTS TO PROCESS BEING SERVED IN ANY SUCH SUIT, ACTION OR PROCEEDING
BY MAILING A COPY THEREOF TO SUCH PARTY AT THE ADDRESS IN EFFECT FOR NOTICES TO
IT UNDER THIS WARRANT AND AGREES THAT SUCH SERVICE SHALL CONSTITUTE GOOD AND
SUFFICIENT SERVICE OF PROCESS AND NOTICE THEREOF. NOTHING IN THIS PARAGRAPH
SHALL AFFECT OR LIMIT ANY RIGHT TO SERVE PROCESS IN ANY OTHER MANNER PERMITTED
BY LAW.

                                       6

<PAGE>

      (c) THIS WARRANT SHALL BE GOVERNED BY AND CONSTRUED AND ENFORCED IN
ACCORDANCE WITH THE INTERNAL LAWS OF THE STATE OF NEW YORK WITHOUT REGARD TO
SUCH STATE'S PRINCIPLES OF CONFLICT OF LAWS.

12.  ENTIRE AGREEMENT: AMENDMENTS.

      This Warrant and the provisions contained in the Agreement and the Rights
Agreement contain the entire understanding of the parties with respect to the
matters covered hereby and thereby and except as specifically set forth herein
and therein, neither the Company nor the Warrant Holder makes any
representation, warranty, covenant or undertaking with respect to such matters.
This Warrant and any term thereof may be changed, waived, discharged or
terminated only by an instrument in writing signed by the party against which
enforcement of such change, waiver, discharge or termination is sought.

13.  NOTICES.

      Any notice or other communication required or permitted to be given
hereunder shall be in writing and shall be effective (a) upon hand delivery or
delivery by telex (with correct answer back received), telecopy or facsimile at
the address or number designated below (if delivered on a business day during
normal business hours where such notice is to be received), or the first
business day following such delivery (if delivered other than on a business day
during normal business hours where such notice is to be received) or (b) on the
second business day following the date of mailing by express courier service,
fully prepaid, addressed to such address, or upon actual receipt of such
mailing, whichever shall first occur. The addresses for such communications
shall be:

         to the Company:

         Cygnus, Inc.
         400 Penobscot Drive
         Redwood City, CA  94063
         Attn: Chief Executive Officer
         Fax:  (650) 369-4300

         with copies to:

         Cygnus, Inc.
         400 Penobscot Drive
         Redwood City, CA  94063
         Attn: General Counsel
         Fax:  (650) 369-4300

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         to the Purchaser:

         Cripple Creek Securities, LLC
         c/o Palladin Group, L.P.
         195 Maplewood Avenue
         Maplewood, New Jersey 07040
         Attn: Robert L. Chender
         Fax: (973) 313-6490

         with copies to:

         Arnold & Porter
         555 12th Street, N.W.
         Washington, D.C.  20004
         Attn: Richard E. Baltz
         Fax:  (202) 942-5999

Either party hereto may from time to time change its address for notices under
this Section 13 by giving at least 10 days prior written notice of such changed
address to the other party hereto.

14.  MISCELLANEOUS.

      This Warrant and any term hereof may be changed, waived, discharged or
terminated only by an instrument in writing signed by the party against which
enforcement of such change, waiver, discharge or termination is sought. The
headings in this Warrant are for purposes of reference only, and shall not limit
otherwise affect any of the terms hereof. The invalidity or unenforceability of
any provision hereof shall in no way affect the validity or enforceability of
any other provisions.

15.  ASSIGNMENT.

      This Warrant may not be assigned, by the Warrant Holder, in whole or in
part, without the prior written consent of the Company; PROVIDED, HOWEVER, that
upon written notice to the Company, the Warrant Holder may assign this Warrant,
in whole or in part, to an Affiliate of the Warrant Holder without the Company's
consent. In either case, to effect a transfer of this Warrant, the Warrant
Holder shall submit this Warrant to the Company together with a duly executed
Assignment in substantially the form and substance of the Form of Assignment
which accompanies this Warrant and, upon the Company's receipt hereof, and in
any event, within three (3) business days thereafter, the Company shall issue a
Warrant to the Warrant Holder to evidence that portion of this Warrant, if any
as shall not have been so transferred or assigned.

                                       8

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Dated:       , 200
      ---- --     -
                                           CYGNUS, INC.



                                           By:
                                              ----------------------------------
                                           Printed:
                                                   ---------------
                                           Title:
                                                 -----------------


Attest:

By:
     ---------------------------------------
Its:
     ---------------------------------------


                           [SIGNATURE PAGE TO WARRANT]

                                       9

<PAGE>
                               SUBSCRIPTION NOTICE
                           (FORM OF WARRANT EXERCISE)
                   (TO BE SIGNED ONLY ON EXERCISE OF WARRANT)

TO _______________

      The undersigned, the holder of the within Warrant, hereby irrevocably
elects to exercise this Warrant:

      (A)   for, and to purchase thereunder, _______________ shares of Common
            Stock of Cygnus, Inc., a Delaware corporation (the "Common Stock"),
            and herewith, or by wire transfer, makes payment of $_____therefor;
            or

 _____(B)   in a "cashless" or "net-issue exercise" for, and to purchase
            thereunder _______________ shares of Common Stock.

      The undersigned requests that the certificates for such shares be issued
in the name of, and

 _____(A)   delivered to ___________________, whose address is
            _____________________; or

 _____(B)   electronically transmitted and credited to the account of
            ______________ undersigned's prime broker (Account
            No. _______________) with Depository Trust Company through its
            Deposit Withdrawal Agent Commission system.


Dated:
      ----------------

--------------
                                       ---------------------------------
                                       (Signature must conform to name of holder
                                       as specified on the face of the Warrant)



                                       ---------------------------------
                                       (Address)

                                       Tax Identification Number:
                                                                  --------------
                                       --------------

                                       10

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                               FORM OF ASSIGNMENT
                 (TO BE SIGNED ONLY ON TRANSFER OF WARRANT)

      For value received, the undersigned hereby sells, assigns, and transfers
unto ______________ the right represented by the within Warrant to purchase ____
shares of Common Stock of Cygnus, Inc., a Delaware corporation, to which the
within Warrant relates, and appoints _________ Attorney to transfer such right
on the books of Cygnus, Inc., a Delaware corporation, with full power of
substitution of premises.


Dated: _______________


                                       ----------------------------------
                                       (Signature must conform to name of holder
                                       as specified on the face of the Warrant)


                                       ----------------------------------
                                                  (Address)

Signed in the presence of:


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


                                       11