NantKwest has dosed the first patient in a Phase II trial of natural killer cells for second and third-line Merkel cell carcinoma (MCC) in patients who are refractory to immune checkpoint inhibitors.

The trial will evaluate the company’s off-the-shelf CD16-targeted natural killer (haNK) cells and ImmunityBio’s IL-15 superagonist N-803 and Avelumab.

The single-arm study will enrol 43 patients who failed all standard of care treatments for MCC, including checkpoint therapy.

NantKwest and ImmunityBio chairman and CEO Patrick Soon-Shiong said: “With over 70% of patients failing checkpoint inhibitors in solid tumours, it is vital to develop novel and effective therapeutic options.

“Checkpoint and CAR-T therapies only target the T-cell, which is a small portion of effector killer cells, and often result in substantial side effects. These side effects make those therapies unusable for many patients.”

The combination therapy by NantKwest has been designed to activate the innate immune system to generate immunological memory against tumours, resulting in immunogenic cell death.

Previous study on non-targeted aNK cells has reported clinical responses either alone or in combination with N-803.

NantKwest adult medical affairs senior vice-president John Lee said: “The current study builds on this approach using a PD-L1 antibody that will bind to the high affinity CD16 receptor on haNK cells to potentially help target PD-L1 tumour cells.

“The N-803 superagonist has been shown to enhance the body’s NK and T cells to also help attack the tumour cells. The goal of this work is to provide real hope for these patients using the power of our combination therapies.”

MCC is a type of skin cancer. Patients with metastatic or locally advanced MCC have an extremely poor prognosis.