OncoSec Medical has announced interim data from KEYNOTE-890, an ongoing Phase 2 study of TAVO™ (intratumoral IL-12) in combination with KEYTRUDA® in patients with heavily pretreated, metastatic, chemotherapy refractory triple negative breast cancer (mTNBC). Patients who previously failed an average of 3.5 prior lines of chemotherapy were enrolled in KEYNOTE-890 to evaluate if the addition of TAVO (IL-12) could provide meaningful clinical activity when combined with KEYTRUDA, an anti-PD-1 checkpoint inhibitor.

Heavily pretreated patients with refractory mTNBC (average of 3.5 prior lines of chemotherapy) showed a rapid tumor reduction of 20% or greater at the initial 3-month evaluation in the first five of 10 patients. Two patients had a partial response, one with a 66% tumor reduction, including a significant reduction of liver lesions, and four patients had stable disease, three of which reported a 20% or greater tumor reduction. These preliminary findings, when compared to the results of KEYNOTE-086, which demonstrated a 5.3% response rate in mTNBC patients treated with KEYTRUDA monotherapy, suggest TAVO's ability to unlock KEYTRUDA's potential anti-cancer efficacy in this very difficult to treat patient population. Four of the six patients who experienced tumor reductions have an ongoing response as of May 9, 2019.

"These interim data are impressive, especially when considering that all of the patients received numerous prior rounds of chemo/radiation with no success, and the safety profile associated with this platform continues to be unparalleled. Metastatic TNBC is a heterogeneous cancer with a poor prognosis where less than five percent of pre-treated patients achieve an objective response to PD-1/PD-L1 checkpoint treatments," said Alain Algazi, M.D., Associate Professor of Clinical Medicine at UCSF and Clinical Strategic Advisor to OncoSec. "Therefore, the marked synergy shown in these patients adds even more support for our earlier findings demonstrating that TAVO primes the tumor microenvironment, dramatically improving the clinical results that would have been anticipated with PD-1/PD-L1 checkpoint treatment alone. The combination of TAVO and KEYTRUDA represents a highly promising new therapeutic approach for TNBC and warrants expedited evaluation."

Of the four patients who progressed following treatment, two received only one cycle of combination treatment prior to rapid clinical deterioration. Importantly, treatment was very well-tolerated, with only three patients reporting Grade 1 TAVO-related adverse events (AE's). No TAVO-related Grade 2 or above AE's/SAE's were reported.

Patients demonstrated encouraging immunological responses in tumor and blood consistent with an IL-12-associated mechanism of action, including on-treatment reduction of the peripheral gMDSC suppressors, which aligns with observed clinical responses. Biomarker analysis of patient tumor and blood samples are ongoing.

The Company has enrolled over half of the targeted enrollment of 25 patients, and expects to complete enrollment and present the clinical data at the San Antonio Breast Cancer Symposium later this year.

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