UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

PURSUANT TO SECTION 13 OR 15(d)

OF THE SECURITIES EXCHANGE ACT OF 1934

Date of Report (Date of earliest event reported): November 9, 2017

SORRENTO THERAPEUTICS, INC.

(Exact Name of Registrant as Specified in its Charter)

4955 Directors Place

San Diego, CA 92121

(Address of Principal Executive Offices) (Zip Code)

Registrant’s telephone number, including area code: (858) 203-4100

N/A

(Former Name, or Former Address, if Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company ¨

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ¨

Item 1.01. Entry into a Material Definitive Agreement.

On November 9, 2017, Sorrento Therapeutics, Inc. (the “Company”) entered into an At Market Issuance Sales Agreement (the “Sales Agreement”) with B. Riley FBR, Inc., as sales agent (the “Agent”), pursuant to which the Company may offer and sell, from time to time, through the Agent (the “Offering”) up to $100,000,000 in shares of its common stock (the “Shares”). Any Shares offered and sold in the Offering will be issued pursuant to the Company’s Registration Statement on Form S-3 filed with the Securities and Exchange Commission (the “SEC”) on November 9, 2017 (the “Form S-3”) and the prospectus relating to the Offering that forms a part of the Form S-3, following such time as the Form S-3 is declared effective by the SEC.

Subject to the terms and conditions of the Sales Agreement, the Agent will use its commercially reasonable efforts to sell the Shares from time to time, based upon the Company’s instructions. Under the Sales Agreement, the Agent may sell the Shares by any method permitted by law deemed to be an “at the market” offering as defined in Rule 415 promulgated under the Securities Act of 1933, as amended (the “Securities Act”).

The Company has no obligation to sell any of the Shares, and may at any time suspend offers under the Sales Agreement. The Offering will terminate upon (a) the election of the Agent upon the occurrence of certain adverse events, (b) 10 days’ notice from one party to the other, or (c) the sale of all of the Shares.

Under the terms of the Sales Agreement, the Agent will be entitled to a commission at a fixed rate of 3.0% of the gross proceeds from each sale of Shares under the Sales Agreement. The Company will also reimburse the Agent for certain expenses incurred in connection with the Sales Agreement, and agreed to provide indemnification and contribution to the Agent with respect to certain liabilities, including liabilities under the Securities Act and the Securities Exchange Act of 1934, as amended.

The Company currently intends to use any net proceeds from the Offering for working capital and general corporate purposes.

The foregoing description of the Sales Agreement does not purport to be complete and is qualified in its entirety by reference to the full text of the Sales Agreement, a copy of which was filed as Exhibit 1.2 to the Form S-3 and is incorporated herein by reference.

This Current Report on Form 8-K shall not constitute an offer to sell or the solicitation of an offer to buy the Shares, nor shall there be any offer, solicitation or sale of the Shares in any state or country in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such state or country.

Item 9.01. Financial Statements and Exhibits.

(d) Exhibits.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.