NantKwest Announces Presentation of Positive Phase 2 Clinical Data of Natural Killer Cell Therapy in Metastatic Merkel Cell Carcinoma at SITC 2019

Durable Responses Demonstrated in 2 of 7 Patients with Refractory Metastatic MCC

Data Supportive of Planned Off-the-Shelf Clinical Trial to Confirm Activity and Safety

CULVER CITY, Calif.–(BUSINESS WIRE)–NantKwest Inc. (Nasdaq: NK), a next generation, clinical-stage immunotherapy company focused on harnessing the unique power of our immune system using natural killer (NK) cells to treat cancer, infectious diseases and other diseases, today announced the presentation of results from their Phase 2 trial investigation using aNK, NantKwest’s off-the-shelf natural killer cell-based therapeutic, in combination with N-803, ImmunityBio’s IL-15 superagonist, in patients with advanced refractory metastatic Merkel cell carcinoma (MCC) (NCT03853317) at The 34^th Annual Meeting of the Society for Immunotherapy for Cancer (SITC 2019) on November 8, 2019 in National Harbor, Maryland. ImmunityBio is an affiliate company of NantKwest.

Dr. Shailender Bhatia, Associate Professor of Medical Oncology at the University of Washington/Fred Hutchinson Cancer Research Center, will make an oral presentation entitled “Final results from a phase 2 study using off-the-shelf activated natural killer (aNK) cells in combination with N-803, an IL-15 superagonist, in patients with metastatic Merkel cell carcinoma (MCC).” That study demonstrated long term, durable responses in 2 of 7 patients with advanced refractory MCC. One of these patients achieved a radiologic complete response, and the second a durable partial response with more than 75% tumor regression and no subsequent therapy (response ongoing to date). Both patients with responses in the trial remain alive to date, 29 and 44 months after the initiation of treatment.

Results from this study provide evidence that treatment with aNK cell therapy can stimulate immune responses to checkpoint inhibitors, even in patients that have previously failed treatments using these types of therapies. One heavily pretreated subject refractory to pembrolizumab was rechallenged with this checkpoint inhibitor subsequent to receiving aNK cell therapy resulting in a durable complete response (CR) that is ongoing at this time, 44 months after receipt of first aNK cell infusion.

“We believe the results of this Phase 2 study are testament to the potential of our natural killer cell-based therapeutics to change the cancer treatment paradigm,” said Dr. Patrick Soon-Shiong, Chairman and CEO of NantKwest. “Long term responses in patients with refractory metastatic disease is a remarkable achievement and is supportive of our upcoming trial, which will evaluate NantKwest’s off-the-shelf CD16-targeted haNK cells in combination with N-803 and Pfizer’s avelumab in patients with advanced MCC who are refractory to immune checkpoint inhibitors. We are particularly enthusiastic about the potential of aNK and N-803 to induce sensitization to checkpoint inhibitors, and thus, are evaluating this in our upcoming trial. We remain deeply committed to harnessing the power of immunogenic cell death across a wide range of indications to provide innovative treatments to patients with serious unmet need.”

Other presentation highlights include:

• Overall response rate of 29% (2 of 7 patients)
• Evidence that aNK cell treatment may induce sensitivity to immune checkpoint inhibitors with a patient previously refractory to pembrolizumab demonstrating an ongoing complete response to the checkpoint inhibitor after completing aNK cell therapy
• aNK cell therapy resulted in increased levels of tumor-infiltrating lymphocytes and increased immune response-related gene expression within tumor tissue
• aNK cells in combination with N-803 were well-tolerated, with no treatment-related serious adverse events or grade ≥3 adverse events
• Infusions all safely administered in the outpatient setting without observed immune related adverse events

Dr. Bhatia said, “Merkel cell carcinoma (MCC) is an aggressive skin cancer that is estimated to be three times more deadly than melanoma. PD-1 blockade works well for around 50 percent of patients with metastatic disease, but a significant proportion do not respond or progress later. Innate immunotherapy approach using aNK cells can potentially overcome resistance mechanisms in PD-1 refractory tumors. I am particularly enthusiastic about the preliminary results of the MCC study, with two complete responses in patients with very advanced metastatic disease.”

About NantKwest

NantKwest (NASDAQ:NK) is an innovative, clinical-stage immunotherapy company focused on harnessing the power of the innate immune system to treat cancer and virally induced infectious diseases. We are the leading producer of clinical dose forms of off-the-shelf Natural Killer (NK) cell therapies. Our activated NK cell platform is designed to destroy cancer and virally infected cells from the body. The safety of our optimized, activated NK cells, as well as their activity against a broad range of cancers, have been tested in phase I clinical trials in Canada and Europe, as well as in multiple phase I and II clinical trials in the United States. By leveraging an integrated and extensive genomics and transcriptomics discovery and development engine, together with a pipeline of multiple, clinical-stage, immuno-oncology programs, NantKwest’s goal is to transform medicine by delivering living drugs in a bag and bringing novel NK cell-based therapies to routine clinical care. NantKwest is a member of the NantWorks ecosystem of companies. For more information, please visit https://nantkwest.com.

haNK is a registered trademark of NantKwest, Inc.

Forward-Looking Statements

This press release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. Forward-looking statements include statements concerning or implying that NantKwest will be successful in improving the treatment of cancer. Risks and uncertainties related to this endeavor include, but are not limited to, obtaining FDA approval of NantKwest’s NK cells as well as other therapeutics as part of the NANT Cancer Vaccine platform as a cancer treatment.

Forward-looking statements are based on management’s current expectations and are subject to various risks and uncertainties that could cause actual results to differ materially and adversely from those expressed or implied by such forward-looking statements. Accordingly, these forward-looking statements do not constitute guarantees of future performance, and you are cautioned not to place undue reliance on these forward-looking statements.

These and other risks regarding NantKwest’s business are described in detail in its Securities and Exchange Commission filings, including in NantKwest’s Quarterly Report on Form 10-Q for the quarter ended September 30, 2019. These forward-looking statements speak only as of the date hereof, and we disclaim any obligation to update these statements except as may be required by law.

Contacts

Jen Hodson

562-397-3639

[email protected]