EXHIBIT 4.3

                                 PROMISSORY NOTE

$8,500,000                                                     December 10, 2001

      FOR VALUE RECEIVED, DISCOVERY LABORATORIES, INC., a Delaware corporation
("Borrower"), hereby promises to pay to the order of PHARMABIO DEVELOPMENT INC.,
a North Carolina corporation ("Lender"), in lawful money of the United States of
America in immediately available funds, the lesser of (i) the principal sum of
Eight Million, Five Hundred Thousand Dollars ($8,500,000) and (ii) the aggregate
unpaid principal amount of all Advances (as defined in the Loan Agreement
referred to below) made by Lender to Borrower pursuant to the Loan Agreement (as
defined below), together with interest accrued thereon. The interest shall
accrue on the unpaid principal amount of each Advance at the rates and in the
manner provided in the Loan Agreement. Payment of the principal amount of this
Note and accrued interest on this Note shall be made at the times and in the
manner provided in the Loan Agreement. Capitalized terms used but not defined
herein shall have the meanings ascribed to them in the Loan Agreement.

      Each Advance made by Lender to Borrower, and all payments made on account
of the principal amount hereof, shall be recorded and endorsed by Lender on the
grid attached hereto which is a part of this Note. Failure to so record and
endorse such Advances and payments, however, shall not affect Borrower's
obligations in respect of such Advances.

      This Promissory Note is the Note referenced in the Loan Agreement between
Borrower and Lender dated as of the date of this Note (as same may be amended
from time to time, the "Loan Agreement"), and is entitled to the benefits of the
Loan Agreement. The Loan Agreement, among other things, (i) provides for the
making of certain Advances by Lender to Borrower from time to time, the
principal amount of each such Advance being a principal amount evidenced by this
Note, and (ii) provides that this Note is secured by, and Borrower has granted a
security interest in, certain of its assets as set forth in that certain
Security Agreement between Borrower and Lender dated as of the same date as this
Note.

      In case an Event of Default shall occur and be continuing and not cured
prior to the expiration of any applicable cure or grace periods set forth in the
Loan Agreement, the unpaid principal amount of, and accrued interest on, this
Note may be declared to be due and payable in the manner and with the effect
provided in the Loan Agreement.

      Borrower hereby waives presentment, demand, notice, protest and all other
demands and notices in connection with the delivery, acceptance, performance and
enforcement of this Note.

      This Note is subject to early termination as set forth in the Loan
Agreement. This Note may be voluntarily prepaid, in whole or in part, on the
terms and conditions set forth in the Loan Agreement. Provided that no Advances
or accrued interest are outstanding and have irrevocably been paid in full and
the Commitment shall have expired or been terminated in accordance with

<PAGE>

the terms of the Loan Agreement, the Lender shall, at the request of Borrower,
promptly, and in no event later than ten (10) Business Days after notice from
Borrower, cancel and return this Note to Borrower.

      This Note shall be governed by and construed in accordance with the law of
the State of Delaware without regard to the conflicts of law rules of such
state.

      This Note may not be assigned by Lender except to an Affiliate of Lender
which agrees in an enforceable written instrument to be bound by all the terms
and conditions of this Note as if it were Lender, which instrument shall be
delivered a reasonably practicable time prior to such assignment.

      Lender and Borrower agree that disputes relating to this Note shall be
subject to the provisions of the Loan Agreement entitled "Internal Review" and
"Arbitration" set forth in Sections 7.15 and 7.16 thereof, respectively.

                                            BORROWER:

                                            DISCOVERY LABORATORIES, INC.


                                            By: /s/ David L. Lopez
                                                --------------------------------
                                            Name: David L. Lopez, Esq.
                                            Title: Vice President, Legal Counsel


                                       2
<PAGE>

                       ADVANCES AND PAYMENTS OF PRINCIPAL

             Amount      Amount of Principal Paid       Unpaid         Notation
  Date     of Advance           or Prepaid         Principal Balance    Made By
  ----     ----------           ----------         -----------------    -------


                                       3