PLAN OF DISTRIBUTION

We are registering the shares of common stock previously issued to permit the resale of these shares of common stock by the holders of the common stock from time to time after the date of this prospectus. We will not receive any of the proceeds from the sale by the selling stockholders of the shares of common stock. We will bear all fees and expenses incident to our obligation to register the shares of common stock.

The selling stockholders may sell all or a portion of the shares of common stock held by them and offered hereby from time to time directly or through one or more underwriters, broker-dealers or agents. If the shares of common stock are sold through underwriters or broker-dealers, the selling stockholders will be responsible for underwriting discounts or commissions or agent’s commissions. The shares of common stock may be sold in one or more transactions at fixed prices, at prevailing market prices at the time of the sale, at varying prices determined at the time of sale or at negotiated prices. These sales may be effected in transactions, which may involve crosses or block transactions, pursuant to one or more of the following methods:

A-3

• on any national securities exchange or quotation service on which the securities may be listed or quoted at the time of sale; • in the over-the-counter market;

• in transactions otherwise than on these exchanges or systems or in the over-the-counter market;

• through the writing or settlement of options, whether such options are listed on an options exchange or otherwise; • ordinary brokerage transactions and transactions in which the broker-dealer solicits purchasers;

• block trades in which the broker-dealer will attempt to sell the shares as agent but may position and resell a portion of the block as principal to facilitate the transaction;

• purchases by a broker-dealer as principal and resale by the broker-dealer for its account; • an exchange distribution in accordance with the rules of the applicable exchange;

• privately negotiated transactions;

• short sales made after the date the Registration Statement is declared effective by the SEC; • sales pursuant to Rule 144;

• agreements between broker-dealers and the selling securityholders to sell a specified number of such shares at a stipulated price per share;

The selling stockholders may also sell shares of common stock under Rule 144 promulgated under the Securities Act of 1933, as amended, if available, rather than under this prospectus. In addition, the selling stockholders may transfer the shares of common stock by other means not described in this prospectus. If the selling stockholders effect such transactions by selling shares of common stock to or through underwriters, broker-dealers or agents, such underwriters, broker-dealers or agents may receive commissions in the form of discounts, concessions or commissions from the selling stockholders or commissions from purchasers of the shares of common stock for whom they may act as agent or to whom they may sell as principal (which discounts, concessions or commissions as to particular underwriters, broker-dealers or agents may be in excess of those customary in the types of transactions involved). In connection with sales of the shares of common stock or otherwise, the selling stockholders may enter into hedging transactions with broker-dealers, which may in turn engage in short sales of the shares of common stock in the course of hedging in positions they assume. The selling stockholders may also sell shares of common stock short and deliver shares of common stock covered by this prospectus to close out short positions and to return borrowed shares in connection with such short sales. The selling stockholders may also loan or pledge shares of common stock to broker-dealers that in turn may sell such shares.

The selling stockholders may pledge or grant a security interest in some or all of the shares of common stock owned by them and, if they default in the performance of their secured obligations, the pledgees or secured parties may offer and sell the shares of common stock from time to time pursuant to this prospectus or any amendment to this prospectus under Rule 424(b)(3) or other applicable provision of the Securities Act amending, if necessary, the list of selling stockholders to include the pledgee, transferee or other successors in interest as selling stockholders under this prospectus. The selling stockholders also may transfer and donate the shares of common stock in other circumstances in which case the transferees, donees, pledgees or other successors in interest will be the selling beneficial owners for purposes of this prospectus.

To the extent required by the Securities Act and the rules and regulations thereunder, the selling stockholders and any broker- dealer participating in the distribution of the shares of common stock may be deemed to be “underwriters” within the meaning of the Securities Act, and any commission paid, or any discounts or concessions allowed to, any such broker-dealer may be deemed to be underwriting commissions or discounts under the Securities Act. At the time a particular offering of the shares of common stock is made, a prospectus supplement, if required, will be distributed, which will set forth the aggregate amount of shares of common stock being offered and the terms of the offering, including the name or names of any broker-dealers or agents, any discounts, commissions and other terms constituting compensation from the selling stockholders and any discounts, commissions or concessions allowed or re-allowed or paid to broker-dealers.

Under the securities laws of some states, the shares of common stock may be sold in such states only through registered or licensed brokers or dealers. In addition, in some states the

• a combination of any such methods of sale; and • any other method permitted pursuant to applicable law.

shares of common stock may not be sold unless such shares have been registered or qualified for sale in such state or an exemption from registration or qualification is available and is complied with.

There can be no assurance that any selling stockholder will sell any or all of the shares of common stock registered pursuant to the registration statement of which this prospectus forms a part.

The selling stockholders and any other person participating in such distribution will be subject to applicable provisions of the Securities Exchange Act of 1934, as amended, and the rules and regulations thereunder, including, without limitation, to the extent applicable, Regulation M of the Exchange Act, which may limit the timing of purchases and sales of any of the shares of common stock by the selling stockholders and any other participating person. To the extent applicable, Regulation M may also restrict the ability of any person engaged in the distribution of the shares of common stock to engage in market-making activities with respect to the shares of common stock. All of the foregoing may affect the marketability of the shares of common stock and the ability of any person or entity to engage in market-making activities with respect to the shares of common stock.

We will pay all expenses of the registration of the shares of common stock pursuant to the registration rights agreement, estimated to be $[ ] in total, including, without limitation, Securities and Exchange Commission filing fees and expenses of

compliance with state securities or “blue sky” laws; provided, however, a selling stockholder will pay all underwriting discounts and selling commissions, if any. We will indemnify the selling stockholders against liabilities, including some liabilities under the Securities Act in accordance with the registration rights agreements or the selling stockholders will be entitled to contribution. We may be indemnified by the selling stockholders against civil liabilities, including liabilities under the Securities Act that may arise from any written information furnished to us by the selling stockholder specifically for use in this prospectus, in accordance with the related registration rights agreements or we may be entitled to contribution.

Once sold under the registration statement, of which this prospectus forms a part, the shares of common stock will be freely tradable in the hands of persons other than our affiliates.

Exhibit 99.1

Sorrento and Conkwest Announce Exclusive Global Collaboration Developing Next Generation Cancer Immunotherapy with “Off-the-Shelf” Chimeric Antigen Receptor–Tumor Attacking Natural Killer (CAR-TNK™) Cell Lines

San Diego and Cardiff-by-the-Sea, CA (Dec. 19, 2014) — Sorrento Therapeutics, Inc. (NASDAQ: SRNE; Sorrento), an oncology

company developing new treatments for cancer and associated pain, and Conkwest, Inc., a privately-held immuno-oncology company developing proprietary Neukoplast® _{(NK-92™), a Natural Killer (NK) cell-line based therapy, announced today that the companies}

have entered into a definitive agreement to jointly develop next generation CAR-TNK™ (pronounced as “Car-Tank”)

immunotherapies for the treatment of cancer. The CAR-TNK technology platform combines Conkwest’s proprietary Neukoplast cell line with Sorrento’s proprietary G-MAB® _{fully human antibody technology and CAR designs to further enhance the potency and}

targeting of Neukoplast. Under the terms of the agreement, Sorrento and Conkwest will establish an exclusive global strategic collaboration focused on accelerating the development of CAR-TNKs for the treatment of hematological malignancies as well as solid tumors. Both companies will jointly own and share development costs and revenues from any developed CAR-TNK products. As part of the transaction, Sorrento will make a $9 million strategic equity investment in Conkwest and provide $2 million in research credit payments towards the development of novel CAR-TNK cell lines.

Adoptive immunotherapy is widely regarded as one of the most impactful and innovative anti-cancer therapy breakthroughs. To date, T-cell based therapies, like CAR-T, have shown the most promise in select hematologic cancers, especially B-cell malignancies such as acute lymphoblastic leukemia (ALL) and chronic lymphocytic leukemia (CLL). They have also demonstrated outstanding therapeutic impact, including a high percentage of complete responses (CRs) in leukemia patients using CD19-CAR-T cells. While the clinical results seen have been promising, CAR-T therapies have been associated with some concerning side effects, especially potentially fatal cytokine-release syndrome that is mediated by interleukin-6 (IL-6) released from the T-cells and characterized by high fevers and sudden drops in blood pressure. Afflicted patients often require aggressive support in an intensive care unit setting. Additionally, most current CAR-T approaches rely upon patient derived T-cells, which require individualized processing, and are thus challenging with regard to commercial scalability, quality control, and consistency. Furthermore, this process relies on the ability to obtain sufficient numbers of the patients’ own immune T-cells to make adequate doses of CAR-T cells.

The “off-the-shelf” CAR-TNK approach will utilize Conkwest’s bioreactor-grown NK-92 cell line, Neukoplast, as the immune effector cells. Among the many features that distinguish Neukoplast from patient derived T-cells are the lack of IL-6 expression (the most common mediator of cytokine release syndrome), an innate capability of destroying a broad range of cancer cells as well as cancer stem cells, and scalability with batch-to-batch consistency. These Neukoplast cells can be re-engineered in a virus-free process to express surface receptors using Sorrento’s G-MAB library to yield a stable line of effector cells that recognize and target specific antigens on tumor cells. The CAR-TNK cells can also be generated and produced in large quantities, thereby obviating the need for

“We are extremely pleased with this strategic collaboration with Conkwest”, said Dr. Henry Ji, President and CEO of Sorrento. “With Sorrento’s expertise in antibody technology and diverse portfolio of fully human antibodies obtained from the G-MAB library, we believe we will be able to generate an army of stable CAR-TNK cell-lines, including but not limited to CD19-CAR-TNK™, PDL1- CAR-TNK™, PSMA-CAR-TNK™, and CD123-CAR-TNK™. It is our goal to rapidly move several of our CAR-TNK cell lines into the clinic to offer patients suffering from hematological malignancies and solid tumors an innovative immunotherapy to fight their cancers.”

“Conkwest has made important strides in establishing the safety and anti-cancer activity of Neukoplast in both pre-clinical and clinical phase I trials” said Dr. Barry Simon, President and CEO of Conkwest. “We have also unlocked the potential of CAR- modified Neukoplast cells in preclinical models. By drawing from Sorrento’s treasure trove of CARs derived from their G-MAB library, we believe this partnership will enable us to realize an important part of our vision of designing and commercializing next generation Neukoplast products re-engineered to express one or more proprietary CARs that would matter most to disease outcomes. We are very excited about this opportunity in joining our resources and talent and look forward to working with the Sorrento team on this next generation of cancer immunotherapies.”

About Sorrento Therapeutics, Inc.

Sorrento is an oncology company developing new treatments for cancer and associated pain. Sorrento’s most advanced asset Cynviloq™, the next-generation nanoparticle paclitaxel, commenced its registrational trial in March 2014 and is being developed under the abbreviated 505(b)(2) regulatory pathway. Sorrento is also developing RTX, a non-opiate TRPV1 agonist currently in a Phase 1/2 study at the NIH to treat terminal cancer patients suffering from intractable pain. The Company has made significant advances in developing human monoclonal antibodies, complemented by a comprehensive and fully integrated ADC platform that includes proprietary conjugation chemistries, linkers, and toxic payloads. Sorrento’s strategy is to enable a multi-pronged approach to combating cancer with small molecules, mono- and bi-specific therapeutic antibodies, ADCs and CAR-TNK cell-lines.

About Conkwest

Conkwest is an innovative immuno-oncology company that is developing and commercializing a portfolio of highly potent and selective cellular therapies for the treatment of cancers and serious viral infections. Conkwest’s products are based on its proprietary cancer-killing cell line, Neukoplast (also known as NK-92) – the only known cell line that can be commercialized as a direct, scalable, off-the-shelf, cancer-killing product. Neukoplast recognizes, binds and directly kills cells expressing stress ligands such as LFA-3, Heparin Sulfate, ICAM-1 and other stress induced proteins commonly found on cancers and virally infected cells. It has demonstrated broad anti-cancer activity both in vitro and in human clinical trials while sparing patients from the serious adverse reactions often seen with CAR-T based therapies. Cancer patients have been treated in phase I clinical trials at RUSH University, Frankfurt AM Main, Princess Margaret Hospital and University of Pittsburgh Cancer Institute. Preparations for the first

U.S. phase II trial in Merkel Cell Carcinoma are currently underway. Conkwest’s universal antibody-targeted CD16-Neukoplast, a re- engineered product which expresses both the high-affinity version of FcgammaR3 (CD16) and ER-IL2 to efficiently target

therapeutic monoclonal antibodies such as Rituxan®_{, Herceptin}® _{and Erbitux}®_{, is presently in the preclinical stage of development.}

Conkwest also commercializes Neukopanel®_{, an NK-92 based bioassay panel for the screening and qualification of therapeutic}

monoclonal antibody products, with revenue bearing licenses to many well-known large pharma and biotechnology companies.

Forward-Looking Statements

This press release contains forward-looking statements related to Sorrento Therapeutics, Inc. under the safe harbor provisions of Section 21E of the Private Securities Litigation Reform Act of 1995 and subject to risks and uncertainties that could cause actual results to differ materially from those projected. Forward-looking statements include statements about the expected achievements of the joint venture with Conkwest; the ability to develop proprietary stable CAR-TNK cell lines; anticipated timing for moving CAR- TNK cell lines into the clinic; Sorrento’s Cynviloq registrational trial; Sorrento’s advances made in developing RTX and human monoclonal antibodies using its proprietary G-MAB fully human antibody technology, if any; and other matters that are described in Sorrento’s Annual Report on Form 10-K for the year ended December 31, 2013, and subsequent Quarterly Reports on Form 10-Q filed with the Securities and Exchange Commission, including the risk factors set forth in those filings. Investors are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date of this release and we undertake no obligation to update any forward-looking statement in this press release except as required by law.

Sorrento Contact:

Mr. George Uy

EVP & Chief Commercial Officer Sorrento Therapeutics, Inc. [email protected] T: + 1 (661) 607-4057

Conkwest Contact:

Ann Marie Fields

Lippert Heilshorn & Associates [email protected]

T: +1 (212) 838-3777

G-MAB, TNK, CAR-TNK, CD19-CAR-TNK, PDL1-CAR-TNK, PSMA-CAR-TNK, and CD123-CAR-TNK are trademarks owned by Sorrento Therapeutics, Inc.