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                                                                Exhibit 10.22

                                   THIRD AMENDMENT
                                          TO
                       REAL ESTATE PURCHASE AND SALE AGREEMENT

    THIS THIRD AMENDMENT TO REAL ESTATE PURCHASE AND SALE AGREEMENT
("Amendment") is made and entered into as January 31, 1997, by and between '1'H
H. PORT OF SEATTLE, a Washington special purpose municipal corporation
("Seller"), and IMMUNEX CORPORATION, a Washington corporation (.Buyer.).

                                       RECITALS

    A. Seller and Buyer entered into a Real Estate Purchase and Sale Agreement
dated as of July 18, 1994, which was amended by First Amendment to Real Estate
Purchase and Sale Agreement dated April 7, 1995 and Second Amendment to Real
Estate Purchase and Sale Agreement dated June 1, 1996 (as amended,
"Agreement".), pursuant to which Seller agreed to sell and Buyer agreed to buy
approximately 29 acres of real property known as Terminal 88, as more
particularly described on EXHIBIT A to the Agreement (."Property"). All
capitalized terms not defined herein shall have the meanings given them in the
Agreement.

    B. Seller and Buyer desire to amend the Agreement as set forth in this
Amendment.

                                      AGREEMENT

    IN CONSIDERATION of the respective agreements hereinafter set forth, Seller
and Buyer agree as follows:

    1. CLOSING DATE. Seller and Buyer acknowledge that, as of the date hereof,
Buyer's Contingencies set forth in Sections 4.3(g)-(h) of the Agreement (among
others) have not been satisfied. The "Closing Date" shall be extended to
December 1, 1997, or such other date prior thereto as Seller and Buyer may agree
to in writing, provided that all of Buyer's Contingencies and Seller's
Contingencies have then been either satisfied or waived in accordance with
Sections 4.3-4.6 of the Agreement. Seller acknowledges that Buyer's
Contingencies set forth in Sections 4.3(b), (c), (d), (e) and (f) have been
satisfied.

    2. CARRYING COSTS. Buyer shall pay to Seller carrying costs for the
Property at the rate of 7.25% of the Purchase Price per annum, compounded
annually, for the period beginning on July 18, 1994 and ending on January 31,
1996. Buyer shall have no obligation to pay carrying costs for the period
beginning on February 1, 1996 and ending on May 31, 1996. Buyer shall pay
carrying costs for the Property at the rate of 3.625% of the Purchase Price per
annum, compounded annually, for the period beginning on June 1, 1996 and ending
on January 31, 1997. Buyer shall have no obligation to pay carrying costs for
the


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Property after January 31, 1997. Buyer shall pay all accrued carrying costs in a
lump sum at closing. Notwithstanding the foregoing, if closing fails to occur
for any reason, Buyer shall have no obligation to pay any carrying costs for the
Property.

    Section 2.3 of the Agreement is hereby deleted. Any references to Section
2.3 of the Agreement shall mean this Section 2 of this Amendment.

    3. EFFECT OF AMENDMENT. Except as set forth in this Amendment, all of the
terms of the Agreement are hereby ratified and confirmed and shall remain in
full force and effect.

    IN WITNESS WHEREOF, the parties hereto have executed this Amendment as of
the date first above written.

  SELLER:     THE PORT OF SEATTLE, a limited purpose
              municipal corporation


              By  /s/  M.R. Dinsmore
              Name  M.R. Dinsmore
              Title  Executive Director


  BUYER:      IMMUNEX CORPORATION, a
              Washington corporation


              By  /s/  D. G. Southern
              Name  D. G. Southern
              Title  Senior Vice President



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