CytomX Therapeutics Announces Treatment of First Patient in Phase 2 Expansion Study of CX-2029, an Anti-CD71 Probody Drug Conjugate

On November 5, 2020 CytomX Therapeutics, Inc. (Nasdaq: CTMX), a clinical-stage oncology-focused biopharmaceutical company pioneering a novel class of investigational antibody therapeutics based on its Probody technology platform, reported the treatment of the first patient in the Phase 2 expansion study of CX-2029, an anti-CD71 Probody drug conjugate (Press release, CytomX Therapeutics, NOV 5, 2020, View Source [SID1234570004]). The study, being conducted under a partnership with AbbVie, is evaluating CX-2029 as monotherapy in four cohorts; squamous non-small cell lung cancer (sqNSCLC), squamous head and neck cancer (sqHNSCC), esophageal cancer, and diffuse large B-cell lymphoma (DLBCL).

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"Our Phase 2 advancement of CX-2029 against the previously undruggable target CD71 marks a major milestone in our broadening clinical pipeline and highlights the progress we continue to make in applying our Probody platform to unique therapeutic opportunities in cancer," said Amy Peterson, MD, chief development officer of CytomX Therapeutics. "These expansion cohorts build on our Phase 1 clinical experience with CX-2029 in which we achieved meaningful therapeutic activity for this first-in-class drug candidate, setting the stage for Phase 2 exploration of its potential."

This open-label, multi-center Phase 2 cohort expansion study (NCT003543813) will enroll approximately 25 evaluable patients in each of the cohorts and assess the efficacy and tolerability of 3 mg/kg of CX-2029 administered every three weeks. The primary objective is overall response rate (ORR) with secondary objectives evaluating safety and tolerability. CytomX anticipates initial data from this study in late 2021.

About the CytomX and AbbVie Collaboration

In April 2016, AbbVie and CytomX entered into a Co-Development and Licensing Agreement under which the two companies are co-developing CX-2029, a Probody drug conjugate against CD71 conjugated to the cytotoxic payload MMAE. CD71, also known as the transferrin receptor 1 ("TfR1"), is a cell surface protein essential for iron uptake in dividing cells. CD71 is highly expressed in a number of solid and hematologic cancers and has attractive molecular properties for efficient delivery of cytotoxic payloads to tumor cells. CD71 has high potential as an anti-cancer target but is widely considered undruggable due to its presence on most dividing healthy cells. CX-2029 is designed to potentially create a therapeutic window for this novel target.

Under the agreement, CytomX is responsible for clinical development up to initial clinical proof of concept. AbbVie will lead late-stage clinical development and global commercial activities with CytomX eligible to receive up to $390 million in development, regulatory and commercial milestone payments, pending the achievement of pre-determined outcomes. In addition, CytomX is eligible to receive a profit share in the U.S. and tiered double-digit royalties on net product sales outside of the U.S. with CytomX retaining an option to co-promote in the U.S. In the first quarter of 2020, CytomX earned a $40 million milestone payment from AbbVie following the achievement of pre-specified criteria for the dose escalation phase of the ongoing Phase 1/2 clinical trial (NCT003543813).