GUARANTY
 
GUARANTY (the “Guaranty”), dated as of September 26, 2007, by Duska Scientific
Co., a Delaware corporation with an address of Duska Therapeutics, Inc., Two
Bala Plaza, Suite 300, Bala Cynwyd, PA (the “Guarantor”), in favor of the
Purchasers identified in the Purchase Agreement (as defined below)
(collectively, “Secured Parties”).

WHEREAS, the Guarantor is a subsidiary or affiliate of Duska Therapeutics, Inc.
(the “Borrower”); and

WHEREAS, in accordance with a certain senior secured convertible note, dated as
of the date hereof (the “Notes”), executed by the Borrower, and certain related
agreements between the Borrower and the Secured Parties (collectively, as
amended, restated, or extended from time to time, the “Loan Documents”), the
Secured Parties have agreed to loan to the Borrower up to Six Million Five
Hundred Thousand Dollars ($6,500,000) (the “Loan”); and

WHEREAS, the Secured Parties’ willingness to extend the loan is conditioned upon
the Guarantor executing and delivering this Guaranty; and

WHEREAS, the aforesaid Loan will be beneficial to the Guarantor inasmuch as the
proceeds of the Loan to the Borrower will indirectly benefit the Guarantor;

NOW, THEREFORE, in order to induce the Secured Parties to make the Loan to the
Borrower pursuant to the Loan Documents, and for other good and valuable
consideration, the receipt and sufficiency of which is hereby acknowledged by
the Guarantor, the Guarantor hereby agrees as follows:

1.  Guaranty of Payment and Performance. The Guarantor hereby guarantees to the
Secured Parties the full and punctual payment when due (whether at maturity, by
acceleration or otherwise), and the performance, of all liabilities, agreements
and other obligations of the Borrower to the Secured Parties, whether direct or
indirect, absolute or contingent, due or to become due, secured or unsecured,
now existing or hereafter arising or acquired (whether by way of discount,
letter of credit, lease, loan, overdraft or otherwise), including without
limitation all obligations under the Note (collectively, the “Obligations”).
This Guaranty is an absolute, unconditional and continuing guaranty of the full
and punctual payment and performance of the Obligations and not of their
collectibility only and is in no way conditioned upon any requirement that the
Secured Parties first attempt to collect any of the Obligations from the
Borrower or resort to any security or other means of obtaining their payment.
Should the Borrower default in the payment or performance of any of the
Obligations, the obligations of the Guarantor hereunder shall become immediately
due and payable to the Secured Parties, without demand or notice of any nature,
all of which are expressly waived by the Guarantor. Payments by the Guarantor
hereunder may be required by the Secured Parties on any number of occasions.

2.  Guarantor’s Agreement to Pay. The Guarantor further agrees, as the principal
obligor and not as a guarantor only, to pay to the Secured Parties, on demand,
all reasonable costs and expenses (including court costs and reasonable legal
expenses) incurred or expended by the Secured Parties in connection with
enforcement of this Guaranty, together with interest on amounts recoverable
under this Guaranty from the time such amounts become due under this Guaranty
until payment, at the rate per annum equal to the default rate set forth in the
Note; provided that if such interest exceeds the maximum amount permitted to be
paid under applicable law, then such interest shall be reduced to such maximum
permitted amount.
 

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3. Unlimited Guaranty. The liability of the Guarantor hereunder shall be
unlimited to the extent of the Obligations and the other obligations of the
Guarantor hereunder (including, without limitation, under Section 2 above).

4. Waivers by Guarantor; Secured Party’s Freedom to Act. The Guarantor agrees
that the Obligations will be paid and performed strictly in accordance with
their respective terms regardless of any law, regulation or order now or
hereafter in effect in any jurisdiction affecting any of such terms or the
rights of the Secured Parties with respect thereto. The Guarantor waives
presentment, demand, protest, notice of acceptance, notice of Obligations
incurred and all other notices of any kind, all defenses which may be available
to Borrower by virtue of any valuation, stay, moratorium law or other similar
law now or hereafter in effect, any right to require the marshalling of assets
of the Borrower, and all suretyship defenses generally. Without limiting the
generality of the foregoing, the Guarantor agrees to the provisions of any
instrument evidencing, securing or otherwise executed in connection with any
Obligation and agrees that the obligations of the Guarantor hereunder shall not
be released or discharged, in whole or in part, or otherwise affected by (i) the
failure of any Secured Party to assert any claim or demand or to enforce any
right or remedy against the Borrower; (ii) any extensions or renewals of any
Obligation; (iii) any rescissions, waivers, amendments or modifications of any
of the terms or provisions of any agreement evidencing, securing or otherwise
executed in connection with any Obligation (provided, that, the obligations of
the Guarantor hereunder shall be appropriately modified to reflect any amendment
or modification of the Obligations); (iv) the substitution or release of any
entity primarily or secondarily liable for any Obligation; (v) the adequacy of
any rights any Secured Party may have against any collateral or other means of
obtaining repayment of the Obligations; (vi) the impairment of any collateral
securing the Obligations, including without limitation the failure to perfect or
preserve any rights a Secured Party might have in such collateral or the
substitution, exchange, surrender, release, loss or destruction of any such
collateral; or (vii) any other act or omission which might in any manner or to
any extent vary the risk of the Guarantor or otherwise operate as a release or
discharge of any other guarantor, all of which may be done without notice to the
Guarantor.

5. Unenforceability of Obligations Against Borrower. If for any reason the
Borrower has no legal existence or is under no legal obligation to discharge any
of the Obligations, or if any of the Obligations have become irrecoverable from
the Borrower by operation of law or for any other reason, this Guaranty shall
nevertheless be binding on the Guarantor to the same extent as if the Guarantor
at all times had been the principal obligor on all such Obligations. In the
event that acceleration of the time for payment of the Obligations is stayed
upon the insolvency, bankruptcy or reorganization of the Borrower, or for any
other reason, all such amounts otherwise subject to acceleration under the terms
of any agreement evidencing, securing or otherwise executed in connection with
any Obligation shall be immediately due and payable by the Guarantor.
 

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6. Subrogation; Subordination. Until the payment and performance in full of all
Obligations, the Guarantor shall not exercise any rights against the Borrower
arising as a result of payment by any Guarantor hereunder, by way of subrogation
or otherwise, and will not prove any claim in competition with any Secured Party
or its affiliates in respect of any payment hereunder in bankruptcy or
insolvency proceedings of any nature; the Guarantor will not claim any set-off
or counterclaim against the Borrower in respect of any liability of the
Guarantor to the Borrower; and the Guarantor waives any benefit of and any right
to participate in any collateral which may be held by any Secured Party. The
payment of any amounts due with respect to any indebtedness of the Borrower now
or hereafter held by the Guarantor is hereby subordinated to the prior payment
in full of the Obligations. The Guarantor agrees that after the occurrence of
any default in the payment or performance of the Obligations, after the
expiration of any applicable cure period, it will not demand, sue for or
otherwise attempt to collect after such time any such indebtedness of the
Borrower to the Guarantor until the Obligations shall have been paid in full.
If, notwithstanding the foregoing sentence, the Guarantor shall collect, enforce
or receive any amounts in respect of such indebtedness, such amounts shall be
collected, enforced and received by the Guarantor as trustee for the Secured
Parties and be paid over to the Secured Parties on account of the Obligations
without affecting in any manner the liability of the Guarantor under the other
provisions of this Guaranty.

7. Further Assurances. The Guarantor agrees to do all such things and execute
all such documents, as a Secured Party may consider reasonably necessary or
desirable to give full effect to this Guaranty and to perfect and preserve the
rights and powers of a Secured Party hereunder.

8. Termination; Reinstatement. This Guaranty shall remain in full force and
effect until the earlier of: (i) the Obligations are paid in full or otherwise
satisfied (including by the conversion in full of the Notes) (other than
contingent indemnity obligations), and not subject to any recapture or
preference in bankruptcy or similar proceedings, and the Secured Parties have no
further commitment to extent credit to the Borrower or (ii) the Secured Parties
are given written notice of the Guarantor’s intention to discontinue this
Guaranty, notwithstanding any intermediate or temporary payment or settlement of
the whole or any part of the Obligations. No such notice under (ii) above shall
be effective against a Secured Party unless received and acknowledged by an
officer of a Secured Party at its head office. Without limiting the generality
of the foregoing sentence, the Guarantor will be released from all liability
hereunder concurrently with either the repayment of in full of all amounts owed
under the Notes or the conversion in full of the Notes. No notice under (ii)
above shall affect any rights of a Secured Party or of any affiliate hereunder
with respect to any Obligations incurred prior to such notice. This Guaranty
shall continue to be effective or be reinstated, notwithstanding any notice or
termination, if at any time any payment made or value received with respect to
an Obligation is rescinded or must otherwise be returned by a Secured Party upon
the insolvency, bankruptcy or reorganization of the Borrower, or otherwise, all
as though such payment had not been made or value received.

9. Successors and Assigns. This Guaranty shall be jointly and severally binding
upon the Guarantor, its successors and assigns, and shall inure to the benefit
of and be enforceable by the Secured Parties and their successors, transferees
and assigns. Without limiting the generality of the foregoing sentence, the
Secured Parties may assign or otherwise transfer any agreement or any note held
by it evidencing, securing or otherwise executed in connection with the
Obligations, or sell participations in any interest therein, to any other person
or entity, and such other person or entity shall thereupon become vested, to the
extent set forth in the agreement evidencing such assignment, transfer or
participation, with all the rights in respect thereof granted to the Secured
Parties herein.
 

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10. Amendments and Waivers. No amendment or waiver of any provision of this
Guaranty nor consent to any departure by the Guarantor therefrom shall be
effective unless the same shall be in writing and signed by the Secured Parties
holding a majority of the principal amount of the Notes. No failure on the part
of a Secured Party to exercise, and no delay in exercising, any right hereunder
shall operate as a waiver thereof; nor shall any single or partial exercise of
any right hereunder preclude any other or further exercise thereof or the
exercise of any other right.

11. Notices. All notices and other communications called for hereunder shall be
made in writing and, unless otherwise specifically provided herein, shall be
deemed to have been duly made or given when delivered by hand or mailed first
class mail postage prepaid or, in the case of telegraphic or telexed notice,
when transmitted, answer back received, addressed as follows: if to the
Guarantor, at the address set forth above, and if to a Secured Party, at the
address set forth in the Purchase Agreement (as defined in the Note).

12. Governing Law; Consent to Jurisdiction. This Guaranty shall be governed by,
and construed in accordance with, the laws of the State of New York without
reference to its conflicts of laws provisions. The Guarantor agrees that any
suit for the enforcement of this Guaranty may be brought in the courts of the
State of New York or any federal court sitting therein and consents to the
non-exclusive jurisdiction of such court and to service of process in any such
suit being made upon the Guarantor by mail at the address specified in Section
11 hereof. The Guarantor hereby waives any objection that it may now or
hereafter have to the venue of any such suit or any such court or that such suit
was brought in an inconvenient court. Any enforcement action relating to this
Guarantee may be brought by motion for summary judgment in lieu of a complaint
pursuant to Section 3213 of the New York Civil Practice Law and Rules.

13. WAIVER OF JURY TRIAL. THE GUARANTOR AND, BY THEIR ACCEPTANCE OF THIS
GUARANTY, EACH SECURED PARTY, HEREBY WAIVES TRIAL BY JURY IN ANY LITIGATION IN
ANY COURT WITH RESPECT TO, IN CONNECTION WITH, OR ARISING OUT OF: (A) THIS
GUARANTY OR ANY OTHER INSTRUMENT OR DOCUMENT DELIVERED IN CONNECTION WITH THE
OBLIGATIONS; (B) THE VALIDITY, INTERPRETATION, COLLECTION OR ENFORCEMENT
THEREOF; OR (C) ANY OTHER CLAIM OR DISPUTE HOWEVER ARISING BETWEEN THE GUARANTOR
AND ANY SECURED PARTY.

14. Certain References. All pronouns and any variations thereof shall be deemed
to refer to the masculine, feminine, neuter, singular or plural, as the identity
of the person, persons, entity or entities may require. The terms “herein”,
“hereof” or “hereunder” or similar terms used in this Guaranty refer to this
entire Guaranty and not only to the particular provision in which the term is
used.

 
15. Miscellaneous. This Guaranty, together with the Security Agreement,
delivered by the Guarantor as of the date hereof to the Secured Parties,
constitutes the entire agreement of the Guarantor with respect to the matters
set forth herein. The rights and remedies herein provided are cumulative and not
exclusive of any remedies provided by law or any other agreement, and this
Guaranty shall be in addition to any other guaranty of the Obligations. The
invalidity or unenforceability of any one or more sections of this Guaranty
shall not affect the validity or enforceability of its remaining provisions.
Captions are for the ease of reference only and shall not affect the meaning of
the relevant provisions. The meanings of all defined terms used in this Guaranty
shall be equally applicable to the singular and plural, masculine, feminine and
generic forms of the terms defined.

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IN WITNESS WHEREOF, the Guarantor has caused this Guaranty to be executed and
delivered as of the date appearing in the introductory paragraph of this
Guaranty.
 
DUSKA SCIENTIFIC CO.
     
By:
/s/ Amir Pelleg        
Name: Amir Pelleg 
Title: President
                   

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