SPECIMEN CERTIFICATE CALLABLE COMMON STOCK The securities of Spiros Development Corporation II, Inc., a Delaware company (the "Company") evidenced hereby are subject to an option of the holder of a majority of the Special Common Stock of the Company, as described in the Amended and Restated Certificate of Incorporation of the Company, to purchase such securities at an agreed upon price, exercisable by notice given at any time beginning on the closing date of the offering of the Callable Common Stock, par value $0.001 per share (the "Callable Common Stock"), of Spiros Development Corporation II, Inc. and the warrants (the "Warrants") to purchase common shares of Dura Pharmaceuticals, Inc. ("Dura") which comprise the Units, (the "Unit Offering") and ending on the earlier of (i) December 31, 2002, (ii) the 90th day after the date the Company provides such holder with quarterly financial statements of the Company showing cash or cash equivalents of less than $5,000,000 or (iii) the date of termination by the Company of that certain Technology License Agreement, Development Agreement or Manufacturing and Marketing Agreement dated on or about December 22, 1997. Copies of the Amended and Restated Certificate of Incorporation of the Company are available at the offices of the Company, 7475 Lusk Boulevard, San Diego, California 92121, Attention: Mitchell R. Woodbury and will be furnished to any shareholder of the Company on request and without cost. Until December 31, 1999 or such earlier date as the Purchase Option is exercised or expires unexercised (the "Separation Date"), the shares of Callable Common Stock represented by this Certificate may be traded, exchanged, or otherwise transferred only together with the Warrant issued herewith. The holder hereof may, but need not, submit this Certificate for the removal of this legend after the Separation Date. SPIROS DEVELOPMENT CORPORATION II, INC. Incorporated Under The Laws of the State of Delaware CALLABLE COMMON STOCK FULLY PAID AND NON-ASSESSABLE CALLABLE COMMON STOCK, PAR VALUE OF $.001 PER SHARE OF SPIROS DEVELOPMENT CORPORATION II, INC. CUSIP 848936100 See Reverse For Certain Definitions THIS CERTIFIES that is the owner of Callable Common Stock of SPIROS DEVELOPMENT CORPORATION II, INC. (the "Company"), transferable on the books of the Company by the holder hereof, in person or by duly authorized attorney, upon surrender of this Certificate properly endorsed. This certificate and the shares represented hereby are subject to the laws of Delaware, and to the Amended and Restated Certificate of Incorporation of the Company as now or hereafter amended (copies of which are on file at the offices of the Company and the Transfer Agent), which are made a part hereof with the same force and effect as if they were set forth herein, to all of which the holder, by acceptance hereof, assents. This certificate is not valid unless countersigned by the Transfer Agent and registered by the Registrar. IN WITNESS WHEREOF, the Company has caused the facsimile signatures of its duly authorized officers and the facsimile of its corporate seal to be hereunto affixed. Dated: Countersigned and Registered: Transfer Agent and Registrar By: ____________________ Name: Title: Authorized Officer Authorized Officer [FORM OF REVERSE OF SPIROS DEVELOPMENT CORPORATION II, INC.'S CALLABLE COMMON STOCK] SPIROS DEVELOPMENT CORPORATION II, INC. The Company will furnish without charge to each shareholder who so requests a copy of the powers, designations, preferences and relative, participating, optional or other special rights of each class of shares of the Company or series thereof, and the qualifications, limitations or restrictions of such preferences and/or rights. The following abbreviations, when used in the inscription on the face of this certificate, shall be construed as though they were written out in full according to applicable laws or regulations: TEN COM - as tenants in common TEN ENT - as tenants by the entireties JT TEN - as joint tenants with right of survivorship and not as tenants in common UNIF GIFT MIN ACT...............Custodian.............................. (cust) (Minor) under Uniform Gifts to Minors Act .................................................... (State) Additional abbreviations may also be used though not in the above list. For Value Received, __________________ hereby sells, assigns and transfers unto Please insert Social Security or other identifying number of assignee Please print or typewrite name and address including postal zip code of assignee Shares represented by the within Certificate, and do hereby irrevocably constitute and appoint attorney, to transfer the said same on the books of the within named Company, with full power of substitution in the premises. Dated: Signature Signature Notice: The signature to this assignment must correspond with the name as written upon the face of the Certificate, in every particular, without alteration or enlargement, or any change whatever. In presence of: Important: All signatures must be guaranteed by a firm which is a financial institution and a member of the Securities Transfer Agent's medallion Program ("STAMP"), the Stock Exchange Medallion Program ("SEMP") or the New York Stock Exchange, Inc. Medallion Signature Program ("MSP"). Signature Guarantee: Name of Firm Authorized Signature Name of Authorized Signatory (Please print) Address of Firm Area Code and Telephone Number of Firm