EXHIBIT 32.1

CERTIFICATION PURSUANT TO 18 U.S.C. SECTION 1350,

ASADOPTED PURSUANT TO SECTION 906 OF THESARBANES-OXLEYACTOF2002

I, Patrick Soon-Shiong, certify, pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that the Annual Report on Form 10-K of NantKwest, Inc. for the fiscal year ended December 31, 2018 fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934 and that information contained in such Annual Report on Form 10-K fairly presents, in all material respects, the financial condition and results of operations of NantKwest, Inc.  

Date: March 13, 2019	By:	/s/ Patrick Soon-Shiong
	Name:	Patrick Soon-Shiong
	Title:	Chief Executive Officer