SAN FRANCISCO – A combination of two novel immune-stimulating agents has shown early evidence of efficacy against malignant melanoma, leiomyosarcoma, and triple-negative breast cancer in a phase 1b, dose-escalating study.
Among 11 evaluable patients enrolled in a trial of NKTR-262, a small molecule agonist of toll-like receptors (TLR) 7/8, and bempegaldesleukin, an interleukin-2 pathway agonist, 2 had a partial response and 3 had stable disease, reported, from the University of Texas MD Anderson Cancer Center, Houston, and his colleagues.
Patients tolerated the combination well, and there have been no serious adverse events or dose-limiting toxicities.
“Pharmacodynamic data demonstrate both activation of the systemic adaptive and the local innate immune system, and we have seen early evidence of clinical activity in patients who are refractory to checkpoint inhibitors with immunotherapy regimens,” Dr. Diab said at the American Society of Clinical Oncology (ASCO) – Society for Immunotherapy of Cancer (SITC): Clinical Immuno-Oncology Symposium.
NKTR-262 is injected into tumors and is designed to be retained in the tumor microenvironment where it helps to activate antigen-presenting cells, such as dendritic cells, and primes development of new, antigen-specific cytotoxic T cells. Bempegaldesleukin is a cytokine that works within the IL-2 pathway to increase CD8-positive T cells and natural killer (NK) cells in the tumor microenvironment.
The rationale for the combination is that NKTR-262 can activate innate immunity in cells surrounding the tumor microenvironment and activate the machinery of antigen-presenting cells, and bempegaldesleukin can prime and boost a systemic tumor immune response that can ultimately mediate antitumor activity in distant lesions, Dr. Adib said.
In preclinical models, the combination of these agents led to a robust antitumor effect that also involved distant lesions through mediation of the abscopal effect, in which treatment of a tumor activates an immune response against distant tumor cells as well, Dr. Diab said.
Theis an ongoing, phase 1b/2 trial looking at the combination in melanoma, Merkel cell carcinoma, triple-negative breast cancer (TNBC), ovarian cancer, renal cell carcinoma, colorectal cancer, urothelial carcinoma, and sarcoma.
The primary goal of the study is to evaluate safety and determine the optimal phase 2 dose of the combination, evaluate biomarkers of response, and assess antitumor activity. As of Jan. 23, 2019, 13 patients were enrolled and evaluable for safety, and 11 were evaluable for the preliminary efficacy analysis.
The most common treatment-related adverse events (TRAEs) with the combination were transient grade 1 or 2 flu-like symptoms, rash, fatigue, pruritus, and nausea. One patients developed grade 3 maculopapular rash and leukocytosis.
Most of the TRAEs are attributable to bempegaldesleukin. There were no immune-mediated AEs and no TRAEs resulted in study discontinuation.
Tumor biopsies obtained 24 hours after injection of NKTR-262 confirmed the activation of TLR 7/8 and robust induction of type 1 interferon, interferon-alpha, and interferon-beta gene-related signatures necessary for optimal antigen presentation.
Dr. Diab noted that in a different trial of bempegaldesleukin monotherapy there was no significant increase in the type 1 interferon gene signature, but the agent did promote activation of the adaptive immune system.
The complementary nature of the two novel agents could also be demonstrated in evaluation of peripheral blood samples, which showed that, although there was no proliferation of T or NK cells following NKTR-262 injection, the addition of bempegaldesleukin resulted in the proliferation of both effector T cells and NK cells to enhance the systemic immune response.
The preliminary efficacy analysis showed that two of five patients with stage IV melanoma who experienced disease progression on prior immune checkpoint inhibitors had partial responses, including one who had a 100% reduction in target lesions and the other with a 50% reduction. In addition, two patients with heavily pretreated leiomyosarcoma had stable disease as the best response, as did the single patient with TNBC.
The maximum tolerated dose of the combination has not been identified, and the investigators are continuing to enroll patients.
The REVEAL study is supported by Nektar Therapeutics. Dr. Diab reported institutional research funding, consulting fees, and advisory board participation from Nektar, Bristol-Myers Squib, Idera Pharmaceuticals, Jounce Therapeutics, and Array BioPharma.
SOURCE: Diab A et al. ASCO-SITC, .