OncoSec Presents Interim Data of 28.5% Objective Response Rate (ORR) from Ongoing KEYNOTE-890 Study Evaluating TAVO™ in Combination with KEYTRUDA® for Heavily Pretreated, Late-Stage, Metastatic Triple Negative Breast Cancer (mTNBC) at the 2019 San Antonio Breast Cancer Symposium

- 4 confirmed partial responses, 3 stable disease as assessed by the investigator in 14 patients who were refractory to chemotherapy and had progressed after an average of three prior lines of therapy

- Previous anti-PD-1 checkpoint studies reported a 6-10% response rate as a monotherapy in a similar but less pretreated (2 prior therapies) patient population

SAN DIEGO and PENNINGTON, N.J., Dec. 13, 2019 /PRNewswire/ -- OncoSec Medical Incorporated ("OncoSec") (Nasdaq:ONCS), a company developing late-stage intratumoral cancer immunotherapies, today announced interim results from KEYNOTE-890, an ongoing Phase 2 study of TAVO™ (intratumoral IL-12) in combination with KEYTRUDA® (pembrolizumab), an anti-PD-1 checkpoint inhibitor, in patients with metastatic, chemotherapy-refractory triple negative breast cancer (mTNBC).

Patients who previously had progressed after an average of three prior lines of chemotherapy were enrolled in the KEYNOTE-890 study to evaluate if the addition of TAVO could provide meaningful clinical activity when combined with KEYTRUDA®.  The interim analysis, presented on December 12, 2019, at the San Antonio Breast Cancer Symposium, included more than half of the patients (14 out of 25) enrolled in the KEYNOTE-890 study evaluating tumor responses, related immunological responses and safety.

Four of the 14 patients showed a rapid tumor reduction and had a confirmed partial response by RECIST v1.1 (ORR 28.5%), including a deep partial response in a patient with multiple liver, bone, skin and nodal metastases and a short disease-free interval following neoadjuvant chemotherapy.  All responses are ongoing (range: 6 to 9 months) and a median duration of response (DOR) has not yet been reached.  Three of the four patients with a partial response experienced deepening tumor shrinkage over six months.

These interim findings compare favorably to the response rate (range of 6-10%) observed with KEYTRUDA as a monotherapy in mTNBC patients 1,2.

Stable disease was observed in three patients (21.4%), with two stable disease patients reporting 20% or greater tumor shrinkage.  Of the seven patients who progressed following treatment, two received only one cycle of combination treatment prior to rapid clinical deterioration.  Regression of both TAVO treated and untreated lesions were observed.  Regression of distal visceral lesions were also observed. Additionally, 3 of the 4 responding patients' lesions were PD-L1 negative by IHC analysis before treatment (1 patient was undetermined).

"Metastatic TNBC is a heterogeneous disease with a poor prognosis where very few pre-treated patients achieve an objective response to PD-1/PD-L1 checkpoint inhibitor therapy," said Melinda L. Telli, MD, Stanford University School of Medicine.  "These preliminary data suggest that TAVO may enhance sensitivity to pembrolizumab in mTNBC patients with a 28.5% ORR reported.  I'm encouraged by the tumor responses observed in PD-L1 negative patients and the overall safety profile."

Importantly, TAVO and pembrolizumab were well tolerated, with only 3 of 16 patients experiencing grade 3 treatment-related adverse events with combination treatment.

Patients demonstrated encouraging immunological responses in tumor and blood consistent with an IL-12-associated mechanism of action, including significantly increased on-treatment proliferating T cell subsets in the periphery and increased gene expression signatures associated with productive immunological responses in the tumor.  Biomarker analysis of patient tumor and blood samples are ongoing.

"These data show a strong signal for clinical benefit with TAVO enhancing sensitivity to pembrolizumab in treating metastatic TNBC patients who were previously unresponsive to multiple prior rounds of therapy," said Kellie Malloy, Chief Clinical Development Officer at OncoSec. "They also confirm the consistent safety profile of TAVO as a well-tolerated cancer immunotherapy.  We look forward to continuing development and plan to expand this clinical program and the KEYNOTE-890 trial."

To date, the KEYNOTE-890 study has enrolled 24 of the planned 25 patients.  OncoSec expects to report the full data results in 2020.

About Triple Negative Breast Cancer (TNBC)

TNBC is an aggressive type of breast cancer that characteristically has a high recurrence rate within the first five years after diagnosis. While some breast cancers may test positive for estrogen receptor, progesterone receptor or human epidermal growth factor receptor 2 (HER2), TNBC tests negative for all three.  As a result, TNBC does not respond to therapies targeting these markers, making it more difficult to treat. Approximately 10-20% of patients with breast cancer are diagnosed with TNBC.

About KEYNOTE-890

KEYNOTE-890 is designed as a multicenter Phase 2 open-label trial focusing on patients with a histologically confirmed diagnosis of inoperable locally advanced or metastatic TNBC and at least 1 prior line of approved systemic chemotherapy or immunotherapy.  25 patients are expected to be enrolled.  Each patient will undergo 3-week treatment cycles with pembrolizumab administered as a 30-minute IV infusion day 1 of every cycle (flat dose of 200 mg) and treated with TAVO on days 1, 5 and 8 every six weeks.

About OncoSec Medical Incorporated 

OncoSec is a clinical-stage biotechnology company focused on developing cytokine-based intratumoral immunotherapies to stimulate the body's immune system to target and attack cancer.  OncoSec has built a deep and diverse clinical pipeline utilizing its primary technology, TAVO™ (tavokinogene telseplasmid) as a potential treatment for multiple cancer indications either as a monotherapy or in combination with leading checkpoint inhibitors; with the latter potentially enabling OncoSec to address a great unmet medical need in oncology: anti-PD-1 non-responders.  In addition to TAVO™, OncoSec is identifying and developing new DNA-encoded therapeutic candidates and tumor indications for use with its new Visceral Lesion Applicator (VLA), to target deep visceral lesions, such as liver, lung or pancreatic lesions. For more information, please visit www.oncosec.com.

TAVO™ is a registered trademark of OncoSec Medical Incorporated.

KEYTRUDA® is a registered trademark of Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc.

  1. ESMO 2019 Congress. KEYNOTE-119: Phase 3 study of pembrolizumab (pembro) versus single-agent chemotherapy (chemo) for metastatic triple-negative breast cancer (mTNBC)
  2. Ann Oncol. 2019 Mar 1;30(3):397-404.   Pembrolizumab monotherapy for previously treated metastatic triple-negative breast cancer: cohort A of the phase II KEYNOTE-086 study.

Forward Looking Statements

Some of the statements included in this press release may be forward-looking statements that involve a number of risks and uncertainties. For those statements, we claim the protection of the safe harbor for forward-looking statements contained in the Private Securities Litigation Reform Act of 1995. The factors that could cause our actual results to differ materially include:  the status, progress and results of our clinical programs; our ability to obtain regulatory approvals for, and the level of market opportunity for our product candidates; our business plans, strategies and objectives, including plans to pursue collaboration, licensing or other similar arrangements or transactions; expectations regarding our liquidity and performance, including expense levels, sources of capital and ability to maintain operations as a going concern; the competitive landscape of our industry; and general market, economic and political conditions; and other risk factors identified from time to time in our reports filed with the Securities and Exchange Commission. Any forward-looking statements set forth in this press release speak only as of the date of this press release. We do not intend to update any of these forward-looking statements to reflect events or circumstances that occur after the date hereof.

Company Contact:
Gem Hopkins
Head of Corporate Communications

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