NantKwest Announces Enhanced High-Affinity Activated Natural Killer (haNK) Cell Therapy in Preclinical Studies of HER2 Positive Breast Cancer at Presentation at the San Antonio Breast Cancer Symposium

CULVER CITY, Calif.–(BUSINESS WIRE)–NantKwest Inc. (Nasdaq:NK), a pioneering, 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 inflammatory diseases, announced that
the company presented results from a preclinical study on the company’s
high affinity Natural Killer (haNK) cell therapy program at the San
Antonio Breast Cancer Symposium (SABCS) in San Antonio, TX, which was
held on December 6-10, 2016.

Previous studies have shown that patients with HER2 positive breast
cancer who have the high-affinity CD16 receptor that have been treated
with Herceptin (trastuzumab) had better clinical outcomes versus those
without the high affinity receptor. In this study, in a mouse xenograft
model of HER2 positive breast cancer, to enhance the activity of aNK
(activated natural killer) cell therapy aNK cells were engineered to
express the CD16 high affinity Fc receptor (haNK cells). Study results
reported provide further supporting evidence that antibody-dependent
cellular cytotoxicity (ADCC) mediated cancer cell killing can be further
enhanced through the recognition of the Fc fragment of a therapeutic
antibody, in this case Herceptin, and the haNK cell’s CD16 Fc receptor.

“In over 50 patients in a broad range of cancer types, NantKwest’s aNK
cell therapy has demonstrated promising indications of efficacy and an
excellent safety record,” said Patrick Soon-Shiong, MD, Chairman and CEO
of NantKwest. “In this study, haNK cell therapy in combination with
Herceptin was highly synergistic, resulting in tumor regression and
significantly better efficacy in comparison to either agent alone. This
data, highlighting the potential benefit of combining haNK cell therapy
with Herceptin in patients with HER2-positive breast cancer, provides
further supportive evidence and a solid foundation to fast track this
program into human clinical trials.”

Collaborating on the study were research scientists from
NantBiosciences, NantCell and NantKwest.

Presentation Summary

• High-affinity Activated Natural Killer (haNK) Cells Augment
  Trastuzumab Efficacy in a Mouse Model of HER2-positive Human
  Metastatic Breast Cancer
• Abstract #P2-04-1-466
• Presenter: Shahrooz Rabizadeh, PhD, NantBiosciences Inc., Culver City,
  CA
• Thursday, December 8, 2016, 7:30 AM, Room Hall 1

This poster reviews the potential synergistic use of haNK cell therapy
in combination with Herceptin (trastuzumab) in patients with
HER2-positive breast cancer.

About NantKwest

NantKwest (Nasdaq:NK) is a pioneering, 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 inflammatory diseases. NK cells are the body’s
first line of defense due to the innate ability of NK cells to rapidly
identify and destroy cells under stress, such as cancer or
virally-infected cells.

NantKwest’s unique NK cell-based platform, with the capacity to grow
active killer cells as a biological cancer therapy, has been designed to
induce cell death against cancer or infected cells by three different
modes of action: (1) Direct killing using activated NK cells (aNK) that
release toxic granules directly into the cell through cell to cell
contact, (2) Antibody-mediated killing using haNKs, which are NK cells
engineered to incorporate a high affinity receptor that binds to an
administered antibody, enhancing the cancer cell killing effect of that
antibody, and (3) Targeted activated killing using taNKs, which are NK
cells engineered to incorporate chimeric antigen receptors (CARs) to
target tumor-specific antigens found on the surface of cancer cells.

Our aNK, haNK and taNK platform addresses certain limitations of T cell
therapies including the reduction of risk of serious “cytokine storms”
reported after T cell therapy. As an “off-the-shelf” therapy,
NantKwest’s NK cells do not rely on a patient’s own often compromised
immune system. In Phase 1 clinical trials in patients with late stage
cancer, NantKwest’s NK cells have been successfully administered as an
outpatient infusion therapy without any reported severe side effects,
even at doses of 10 billion cells.

By leveraging an integrated and extensive genomics and transcriptomics
discovery and development engine, together with a pipeline of multiple,
clinical-stage, immuno-oncology programs that include a Phase 2 trial
for a rare form of melanoma and the planned initiation of a clinical
trial of NK cells targeted to breast cancer, we believe NantKwest is
uniquely positioned to be the premier immunotherapy company and
transform medicine by delivering living drugs in a bag and bringing
novel NK cell-based therapies to routine clinical care. For more
information, please visit http://www.nantkwest.com.

Contacts

NantKwest Inc.
Jen Hodson, 562-397-3639
jhodson@nantworks.com