CytomX Therapeutics, Inc. (Nasdaq: CTMX), a leader in the field of
conditionally activated oncology therapeutics, today announced that
the Phase 2 study of praluzatamab ravtansine in patients with
hormone receptor-positive (HR+)/human epidermal growth factor
receptor 2 (HER2)-non-amplified breast cancer (Arm A) met its
primary efficacy endpoint of confirmed objective response rate
(ORR) of greater than 10 percent by central radiology review.
Praluzatamab ravtansine is a DM4-conjugated, conditionally
activated antibody-drug conjugate (ADC) targeting CD166 and is
wholly owned by CytomX.
As of the data cutoff on May 13, 2022, 47
patients unselected for CD166 expression with advanced
HR+/HER2-non-amplified breast cancer were evaluable for the primary
efficacy endpoint. The ORR by central radiology review was 15
percent. Clinical benefit rate at 24 weeks by investigator (CBR24),
as defined in the protocol as any response (confirmed or
unconfirmed) or stable disease for 24 weeks, was 40 percent; median
progression-free survival was 2.6 months. All patients in Arm A
were treated at the initial Phase 2 starting dose of 7 mg/kg
administered every three weeks. Arm B did not pass protocol-defined
futility boundary (ORR was less than 10%) in patients with advanced
triple-negative breast cancer (TNBC) and enrollment into Arms B and
C will be discontinued.
As of this data cut, the safety profile of
praluzatamab ravtansine in Arm A was generally consistent with
toxicities observed in Phase 1 and with the DM4 payload; namely,
high-grade toxicities or toxicities resulting in dose modifications
were predominantly ocular or neuropathic in nature. Thirty percent
of patients discontinued treatment for an adverse event (AE). Grade
3+ ocular and neuropathic toxicities were 15 and 10 percent,
respectively. Arm B evaluated both 7 mg/kg and 6 mg/kg in patients
with TNBC. The toxicity profile of 7 mg/kg starting dose was
consistent with Arm A. In the 6 mg/kg cohort, no patients
discontinued treatment for an AE and Grade 3+ ocular or neuropathic
related events were lower at 3, and 0 percent, respectively.
Biomarker analysis is ongoing. CytomX intends to submit data from
this study for presentation at a medical conference in the second
half of 2022.
“These results from our Phase 2 evaluation of
praluzatamab ravtansine support single-agent activity of this novel
drug candidate in hormone receptor-positive breast cancer where
significant unmet need remains,” said Sean McCarthy, D.Phil., chief
executive officer and chairman at CytomX Therapeutics. “However, we
do not believe the median progression-free survival at 7 mg/kg
supports further evaluation at this dose. While we are encouraged
by the emerging safety profile of 6 mg/kg, we do not plan to
further advance this program alone given current financial market
conditions and will be seeking a partnership.”
Kathy D. Miller, MD, Ballvé Lantero Professor of
Oncology, Indiana University Simon Comprehensive Cancer Center,
Indianapolis, Indiana, and lead investigator of the Phase 2 study
stated, “In this Phase 2 study, praluzatamab ravtansine showed
single-agent activity in an unselected population of patients with
advanced HR+/HER2-non-amplified breast cancer; additional clinical
studies at 6 mg/kg are warranted.”
Conference Call &
WebcastCytomX management will host a conference call and a
simultaneous webcast today at 5:00 pm ET (2:00 pm PT) to discuss
these results. Participants may register for the conference call
here and are advised to do so at least 10 minutes prior to joining
the call. A live webcast of the call can be accessed via the Events
and Presentations page of CytomX's website at
https://ir.cytomx.com/events-and-presentations.
About Praluzatamab
RavtansinePraluzatamab ravtansine is a conditionally
activated antibody-drug conjugate (ADC) comprised of a
CD166-directed humanized monoclonal antibody conjugated to the
maytansinoid DM4, a tubulin inhibitor. Praluzatamab ravtansine
utilizes CytomX Probody® platform technology, which incorporates a
masking peptide to cover and block the cellular binding region of
the antibody. Tethered to the antibody via a protease-cleavable
linker, the masking peptide is designed to be removed in a
protease-rich tumor microenvironment, enabling the ADC to be
unmasked and engage its target to deliver the toxic DM4 payload
inside tumor cells. The goal is to have praluzatamab ravtansine
remain inert while in circulation to limit binding in healthy
tissues until it is activated by tumor-associated proteases.
Praluzatamab ravtansine was evaluated in a three-arm Phase 2 study
(NCT04596150) in patients with hormone
receptor-positive/HER2-non-amplified breast cancer and patients
with triple-negative breast cancer.
About the Phase 2 Study of Praluzatamab
Ravtansine in Breast Cancer
(NCT04596150) Arm A of
the study evaluated praluzatamab ravtansine as monotherapy (7
mg/kg, Q3W) in patients with inoperable, locally advanced or
metastatic hormone receptor-positive/human epidermal growth factor
receptor 2 (HER2)-non-amplified breast cancer. Patients received 0
to 2 prior cytotoxic chemotherapies in the inoperable, locally
advanced, or metastatic setting, regardless of the level of CD166
expression.
Arm B assessed praluzatamab ravtansine as a
single agent (6 or 7 mg/kg, Q3W) in patients with inoperable,
locally advanced or metastatic triple-negative breast cancer
(TNBC). Patients received 1 to 3 prior lines of chemotherapy for
inoperable, locally advanced, or metastatic disease and had CD166
expression.
Arm C studied praluzatamab ravtansine (6 mg/kg,
Q3W) in combination with pacmilimab (1200 mg, Q3W), CytomX’s
proprietary conditionally activated anti-PD-L1 antibody, in
patients with TNBC. Eligibility was the same as Arm B with the
additional requirement that patients’ tumors were programmed
death-ligand 1 (PD-L1)-positive by an FDA-approved test.
About CytomX Therapeutics,
Inc.CytomX is a clinical-stage, oncology-focused
biopharmaceutical company dedicated to destroying cancer
differently. By pioneering a novel class of conditionally activated
biologics, powered by its Probody® technology platform, CytomX’s
goal is to transcend the limits of current cancer treatments by
successfully leveraging therapeutic targets that were once thought
to be inaccessible. CytomX’s robust and differentiated pipeline
includes the wholly-owned praluzatamab ravtansine, an
investigational conditionally activated antibody-drug conjugate
(ADC) directed toward CD166, and CX-2029, an investigational
conditionally activated ADC directed toward CD71 being developed in
collaboration with AbbVie. These two programs are currently being
evaluated in Phase 2 studies, targeting a variety of late-stage,
difficult-to-treat cancer types, including breast cancer for
praluzatamab ravtansine, and squamous non-small cell lung cancer,
and head and neck squamous cell carcinoma for CX-2029. CytomX’s
clinical pipeline also includes cancer immunotherapeutic candidates
against validated targets such as the CTLA-4-targeting Probody
therapeutics, BMS-986249 and BMS-986288, partnered with Bristol
Myers Squibb, and our wholly-owned conditionally activated
anti-PD-L1 antibody, pacmilimab, as well as CX-904, a conditionally
activated T-cell-engaging bispecific antibody targeting the
epidermal growth factor receptor on tumor cells and the CD3
receptor on T cells, which is partnered with Amgen. In addition,
CytomX has a diverse preclinical portfolio and strategic
collaborations with multiple leaders in oncology, including AbbVie,
Amgen, Astellas, and Bristol Myers Squibb. For more information
about CytomX and how it is working to make conditionally activated
treatments the new standard-of-care in the fight against cancer,
visit www.cytomx.com and follow us on LinkedIn and Twitter.
Forward-Looking StatementsThis
press release includes forward-looking statements. Such
forward-looking statements involve known and unknown risks,
uncertainties and other important factors that are difficult to
predict, may be beyond our control, and may cause the actual
results, performance or achievements to be materially different
from any future results, performance or achievements expressed or
implied in such statements. Accordingly, you should not rely on any
of these forward-looking statements, including those relating to
the potential benefits, safety and efficacy or progress of CytomX’s
or any of its collaborative partners’ other product candidates,
including praluzatamab ravtansine, the potential benefits or
applications of CytomX’s Probody platform technology, CytomX’s
ability to develop and advance product candidates into and
successfully complete clinical trials, including the ongoing
clinical trial of praluzatamab ravtansine, CX-2029, BMS-986249,
BMS-986288, pacmilimab, and CX-904, the timing of ongoing data
availability, and our ability to obtain a partner for praluzatamab
ravtansine. Risks and uncertainties that contribute to the
uncertain nature of the forward-looking statements include: the
unproven nature of CytomX’s novel Probody Platform technology;
CytomX’s clinical trial product candidates are in the initial
stages of clinical development and its other product candidates are
currently in preclinical development, and the process by which
preclinical and clinical development could potentially lead to an
approved product is long and subject to significant risks and
uncertainties, including the risk that the COVID-19 worldwide
pandemic may continue to negatively impact the business, research
and clinical operations of CytomX or its partners, including the
development of preclinical drug candidates due to delays in and
disruption of research activities and the development of clinical
drug candidates due to delays in or disruption of clinical trials,
including impacts on the enrollment of patients in clinical trials
or other clinical trial disruptions; the possibility that the
results of early clinical trials may not be predictive of future
results; the possibility that CytomX’s clinical trials will not be
successful; the possibility that current preclinical research may
not result in additional product candidates; CytomX’s dependence on
the success of praluzatamab ravtansine, CX-2029, BMS-986249,
BMS-986288, pacmilimab, and CX-904; CytomX’s reliance on third
parties for the manufacture of the Company’s product candidates;
and possible regulatory developments in the United
States and foreign countries. Additional applicable risks and
uncertainties include those relating to our preclinical research
and development, clinical development, and other risks identified
under the heading "Risk Factors" included in CytomX’s Quarterly
Report on Form 10-Q filed with the SEC on May 5,
2022. The forward-looking statements contained in this press
release are based on information currently available to CytomX and
speak only as of the date on which they are made. CytomX does not
undertake and specifically disclaims any obligation to update any
forward-looking statements, whether as a result of any new
information, future events, changed circumstances or otherwise.
Probody is a U.S. registered trademark of CytomX Therapeutics,
Inc.
Investor Contact:Chau Cheng, PhD MBAVP,
Investor Relations & Corp.
Communicationsccheng@cytomx.com Direct: (650) 273-4999
Media Contact:Bret CoonsDirector, Corporate
Communicationsbcoons@cytomx.com Direct: (650) 528 2929
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