Phio Pharmaceuticals (PHIO) 10-Q 2013 Q1 Quarterly report

Exhibit 32.1

CERTIFICATION PURSUANT TO

18 U.S.C. SECTION 1350

AS ADOPTED PURSUANT TO

SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

In connection with the Quarterly Report of RXi Pharmaceuticals Corporation (the “Company”) on Form 10-Q for the period ended March 31, 2013 as filed with the Securities and Exchange Commission on the date hereof (the “Report”), the undersigned officer of the Company certifies, pursuant to 18 U.S.C. § 1350, as adopted pursuant to § 906 of the Sarbanes-Oxley Act of 2002, that to his knowledge:

1. The Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934; and

2. The information contained in the Report fairly presents, in all material respects, the Company’s financial condition and result of operations.

/s/ Geert Cauwenbergh

Geert Cauwenbergh, Dr. Med. Sc.

President, Chief Executive Officer and Chief Financial Officer

(as Principal Executive and Financial Officer)

May 15, 2013