CytomX Therapeutics Provides Update on Anti-PD-L1 Probody CX-072 at 2019 ASCO Annual Meeting

- Monotherapy Expansion Cohorts Show Clinical Activity Across Multiple Cancer Types -

- Differentiated Safety Profile Continues to Emerge -

SOUTH SAN FRANCISCO, CA, USA I June 01, 2019 I 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, today presented additional results from PROCLAIM-072, an ongoing Phase 1/2 trial evaluating CX-072, a Probody therapeutic targeting PD-L1. 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) in Chicago, Illinois.

“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

About CytomX Therapeutics

CytomX Therapeutics is a clinical-stage oncology-focused biopharmaceutical company pioneering a novel class of investigational antibody therapeutics based on its Probody™ therapeutic technology platform. Probody therapeutics are designed to exploit unique conditions of the tumor microenvironment to more effectively localize antibody binding and activity while minimizing activity in healthy tissues. CytomX and its partners have four programs in the clinic.  The Company’s clinical stage pipeline includes cancer immunotherapies against clinically validated targets, including a PD-L1-targeting Probody therapeutic wholly owned by CytomX (CX-072) and a CTLA-4-targeting Probody therapeutic partnered with Bristol Myers Squibb (BMS-986249). The Company’s clinical stage pipeline also includes first-in-class Probody drug conjugates against highly attractive targets, including a CD166-targeting Probody drug conjugate wholly owned by CytomX (CX-2009), and a CD71-targeting Probody drug conjugate partnered with AbbVie (CX-2029). CD166 and CD71 are among cancer targets that are considered to be inaccessible to conventional antibody drug conjugates due to their presence on many healthy tissues. In addition to its wholly owned programs, CytomX has strategic collaborations with AbbVie, Amgen, Bristol-Myers Squibb Company and ImmunoGen, Inc. For more information, visit www.cytomx.com.

SOURCE: CytomX Therapeutics

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