Exhibit 99.1

PRELIMINARY PROXY CARD SUBJECT TO COMPLETION, DATED JANUARY 29, 2021 NANTKWEST, INC. NANTKWEST, INC. SPECIAL MEETING OF STOCKHOLDERS Date: March 8, 2021 Time: 9:30 a.m. (Pacific Time) Webcast Address: Special Meeting to be held live via internet—please visit www.proxydocs.com/NK for more details. Please make your marks like this: Use dark black pencil or pen only The Board of Directors Recommends a Vote FOR proposal 1, FOR proposal 2, and FOR proposal 3. Directors For Against Abstain Recommend 1: common To approve stock the issuance to security of holders shares of of NantKwest ImmunityBio For as “stock contemplated issuance proposal”) by the merger . agreement (the For Against Abstain 2: merger To approve agreement the merger (the contemplated “merger proposal”) by the. For For Against Abstain 3: To special approve meeting the adjournment to a later date of or the dates, NantKwest For if and necessary, vote of proxies to permit in the further event solicitation that there connection are insufficient with, votes the approval for, or otherwise of the stock in issuance “adjournment proposal proposal”) or the .merger proposal (the THE SHARES REPRESENTED BY THIS PROXY WILL BE VOTED AS DIRECTED OR, IF NO DIRECTION IS GIVEN, SHARES WILL BE VOTED FOR THE STOCK ISSUANCE PROPOSAL, FOR THE MERGER PROPOSAL, AND FOR THE ADJOURNMENT PROPOSAL. TO ATTEND the Special Meeting of NantKwest, Inc., please visit www.proxydocs.com/NK for virtual meeting registration details. Authorized Signatures—This section must be completed for your Instructions to be executed. Please Sign Here Please Date Above Please Sign Here Please Date Above Please sign exactly as your name(s) appears on your stock certificate. If held in joint tenancy, all persons should sign. Trustees, administrators, etc., should include title and authority. Corporations should provide full name of corporation and title of authorized officer signing the proxy. Please separate carefully at the perforation and return just this portion in the envelope provided. Special Meeting of Stockholders March 8, 2021 This proxy is being solicited by the Board of Directors VOTE BY: INTERNET TELEPHONE Call www. Go To proxypush.com/NK 866-249-5381 Cast your vote online. • Use any touch-tone telephone. • OR • Have your Proxy Card/Voting Instruction Form ready. • Have your Proxy Card/Voting Instruction Form ready. • Follow the simple recorded instructions. MAIL OR • Mark, sign and date your Proxy Card/Voting Instruction Form. • Detach your Proxy Card/Voting Instruction Form. • Return your Proxy Card/Voting Instruction Form in the postage-paid envelope provided. The undersigned hereby appoints Richard Adcock and Sonja Nelson, and each of them as proxies for the undersigned, with full power of substitution, to vote all the shares of common stock of NantKwest, Inc., the undersigned is entitled to vote at the Special Meeting of Stockholders of NantKwest, Inc., which is being held live via internet webcast at www.proxydocs.com/NK, at 9:30 a.m., Pacific Time on March 8, 2021, and any adjournment or postponement thereof upon the matters specified herein and upon such other matters as may be properly brought before the meeting or any adjournment or postponement thereof, conferring authority upon such proxies to vote in their discretion on such other matters as may properly come before the meeting and revoking any proxy heretofore given. PROXY TABULATOR FOR NANTKWEST, INC. P.O. BOX 8016 CARY, NC 27512-9903

Please separate carefully at the perforation and return just this portion in the envelope provided. Proxy — NantKwest, Inc. Special Meeting of Stockholders March 8, 2021 at 9:30 a.m., Pacific Time This Proxy is Solicited by the Board of Directors for use at the Special Meeting on March 8, 2021 The undersigned appoints Richard Adcock and Sonja Nelson, and each of them as proxies for the undersigned, with full power of substitution, to vote all the shares of common stock of NantKwest, Inc., the undersigned is entitled to vote at the Special Meeting of Stockholders of NantKwest, Inc., to be held live via internet webcast at www.proxydocs.com/NK, on March 8, 2021 at 9:30 a.m. Pacific Time or any adjournments or postponement thereof. This proxy, when properly executed, and timely returned will be voted in the manner indicated on the reverse side. If no direction is made, this proxy will be voted “FOR” the stock issuance proposal, “FOR” the merger proposal, and “FOR” the adjournment proposal. In their discretion, to the extent permitted by rule 14a-4(c) under the Securities Exchange Act of 1934, as amended, the proxies are authorized to vote upon such other matters that may properly come before the Special Meeting or any adjournment or postponement thereof. You are encouraged to specify your choice by marking the appropriate box (SEE REVERSE SIDE) but you need not mark any box if you wish to vote in accordance with the Board of Directors’ recommendation. The proxies named above cannot vote your shares unless you sign and return this card. To be signed and dated on Reverse side See Reverse side for voting instructions