EXHIBIT 5 OPINION AND CONSENT OF FISHER THURBER LLP April 16, 1998 Vyrex Corporation 2159 Avenida de la Playa La Jolla, CA 92037 Dear Sirs: We refer to the Registration Statement on Form S-8 (the "Registration Statement") to be filed with the Securities and Exchange Commission under the Securities Act of 1933, as amended (the "Act"), on behalf of Vyrex Corporation, a Nevada corporation (the "Company"), relating to 2,875,00 shares of the Company's Common Stock, $.001 par value (the "Common Stock"), to be issued pursuant to the Vyrex Corporation 1993 Stock Option Plan (the "Plan"). As counsel to the Company, we have examined such corporate records, other documents and such questions of law as we have deemed necessary or appropriate for the purposes of this opinion and, upon the basis of such examinations, advise you that in our opinion all necessary corporate proceedings by the Company have been duly taken to authorize the issuance of the Common Stock pursuant to the Plan and the shares of Common Stock being registered pursuant to the Registration Statement, when issued and paid for in accordance with the terms of the Plan, will be duly authorized, validly issued, fully paid and non-assessable. We consent to the filing of this opinion as Exhibit 5 to the Registration Statement. This consent is not to be construed as an admission that we are a person whose consent is required to be filed with the Registration Statement under the provisions of the Act. Very truly yours, /s/ David A. Fisher David A. Fisher DAF:nxm