On June 1, 2019 CytomX Therapeutics, Inc. (Nasdaq: CTMX), a clinical-stage oncology-focused biopharmaceutical company pioneering a novel class of investigational antibody therapeutics based on its Probody therapeutic technology platform, reported additional results from PROCLAIM-072, an ongoing Phase 1/2 trial evaluating CX-072, a Probody therapeutic targeting PD-L1 (Press release, CytomX Therapeutics, JUN 1, 2019, View Source [SID1234536751]). Data from the ongoing CX-072 monotherapy expansion cohorts (Part D) were presented this morning in a poster and will be presented this afternoon in a poster discussion at the 2019 Annual Meeting of the American Society of Clinical Oncology (ASCO) (Free ASCO Whitepaper) in Chicago, Illinois.

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"The breadth of anti-cancer activity of CX-072 monotherapy has continued to come into focus as these initial expansion cohorts have advanced," said Sean McCarthy D.Phil., president, chief executive officer and chairman of CytomX Therapeutics. "Furthermore, the differentiated safety profile that is emerging for this unique agent is consistent with our vision for CX-072 to become a foundation for safer and potentially more effective combination therapies."

CX-072, a PD-L1 Probody Therapeutic, as Monotherapy in Patients with Advanced Solid Tumors: Preliminary Results of PROCLAIM-CX-072

Session: Developmental Immunotherapy and Tumor Immunobiology (Poster #157)

Presenter: Aung Naing, M.D., FACP, The University of Texas MD Anderson Cancer Center

The PROCLAIM-CX-072 monotherapy Part D phase is examining safety and efficacy of CX-072 at 10 mg/kg every 2 weeks in multiple selected tumor types. Data was reported in patients with triple negative breast cancer (TNBC), anal squamous cell carcinoma (SCC), cutaneous squamous cell carcinoma (cSCC), undifferentiated pleomorphic sarcoma (UPS), and small bowel adenocarcinoma (SBA).

CX-072 Demonstrates Durable Anti-Tumor Activity

As of an April 5, 2019 data cutoff, 72 patients were enrolled and treated across the five reported cohorts. Among the 65 patients evaluable for efficacy, confirmed partial responses were observed in two patients with TNBC, one in a cSCC patient, and one in a UPS patient. A partial response, unconfirmed at the time of data cutoff, was subsequently confirmed in an anal SCC patient. These data resulted in disease control rates of 53% (8/15) in TNBC, 58% (7/12) in anal SCC, 67% (4/6) in cSCC, 25% (5/20) in UPS, and 17% (2/12) in SBA. Decreases in target lesion size were observed in the first 8 to 16 weeks of treatment. Responding patients remained on CX-072 for up to 72 weeks. Patients enrolled were generally heavily pretreated with a median number of three prior regimens before receiving CX-072.

CX-072 Monotherapy Well Tolerated

As of the data cutoff, CX-072 monotherapy was generally well tolerated with a favorable overall safety profile. Of the 72 patients evaluable for safety, 6% of patients experienced a grade ≥3 treatment related adverse event (TRAE), and 3% experienced grade ≥3 immune related adverse events (irAEs) with no (0%) TRAEs leading to treatment discontinuation.

A copy of this poster is available in the Scientific Publications section of the CytomX website at www.CytomX.com.

This poster will be reviewed this afternoon as part of the Developmental Immunotherapy and Tumor Immunobiology Poster Discussion Session.

Presenter: David B. Page, M.D., Providence Cancer Center
Date/Time: Saturday, June 1, 1:15 – 2:45 p.m.
Location: McCormick Place, Hall D1