On March 12, 2019 Scholar Rock Holding Corporation (NASDAQ:SRRK), a clinical-stage biopharmaceutical company focused on the treatment of serious diseases in which protein growth factors play a fundamental role, reported that it has selected SRK‑181, a highly specific inhibitor of TGFβ1 activation, as the first product candidate in its TGFβ1 cancer immunotherapy program based on the strength of its preclinical data and human translational insights (Press release, Scholar Rock, MAR 12, 2019, View Source [SID1234537354]). Scholar Rock has initiated manufacturing and is progressing preclinical development efforts with plans to initiate a Phase 1 trial in patients with solid tumors in mid- 2020.
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"Given that a majority of cancer patients fail to respond to checkpoint blockade therapies, we are eager to advance the next product candidate from our pipeline of growth factor modulators to potentially address a key mechanism of pre-existing resistance," said Nagesh Mahanthappa, Ph.D., President and CEO of Scholar Rock. "A growing body of evidence strongly implicates elevated TGFβ1 activity as a cause of immunotherapy failure, and we see tremendous potential for SRK-181 to expand the number of patients who could benefit from checkpoint blockade therapies by potently and selectively inhibiting the activation of TGFβ1."
SRK-181 is a fully human antibody designed to bind to, and prevent the activation of, latent TGFβ1 with high affinity and high selectivity, as evidenced by minimal or no binding to latent TGFβ2 and latent TGFβ3 isoforms. Several important factors led to the decision to advance SRK-181 as a clinical development product candidate for the treatment of tumors resistant to checkpoint blockade therapies (CBTs), such as anti-PD1 antibodies. These factors include:
TGFβ signaling has been implicated as a culprit in primary resistance to CBTs in multiple peer-reviewed studies.
Translational data analyses by Scholar Rock highlight the prominent expression of TGFβ1 in many human tumor types, such as bladder cancer, non-small cell lung cancer and melanoma, for which CBTs have either been approved or demonstrated clinical activity in trials.
Clinical correlation and preclinical model data suggest that TGFβ1 excludes effector cell entry into the tumor, thereby limiting immune system access to tumor cells.
Preclinical studies in syngeneic mouse tumor models resistant to CBT show SRK-181-mIgG1 (the murine version of SRK-181), when combined with anti-PD1 antibodies, permitted effector T cell infiltration and expansion into the tumor microenvironment and led to tumor regression or control as well as significant survival benefit.
A 28-day pilot toxicology study of SRK-181 in adult rats showed no observed drug-related toxicity up to a weekly dose of 100 mg/kg for 4 weeks.
Detailed preclinical results for SRK-181-mIgG1 (formerly referred to as SRTβ1-Ab3) were presented at the Society for Immunotherapy of Cancer (SITC) (Free SITC Whitepaper) 33rd Annual Meeting in November 2018. The poster presented at SITC (Free SITC Whitepaper) can be accessed by visiting the Scholar Rock website at View Source Additional preclinical data for SRK-181-mIgG1 will be presented at the 2019 American Association for Cancer Research (AACR) (Free AACR Whitepaper) Annual Meeting scheduled to take place March 29 to April 3, 2019 in Atlanta, GA.
About SRK-181
SRK-181 is a highly specific inhibitor of TGFβ1 activation being developed to overcome primary resistance to checkpoint blockade therapies (CBTs). TGFβ1 is the predominant TGFβ isoform expressed in many human tumors, particularly for those tumors where checkpoint therapies are currently approved. Based on analyses of human tumors that are resistant to CBT, TGFβ1 is implicated as a key contributor to exclude immune cell entry into the tumor microenvironment, thereby preventing normal immune function. By overcoming this immune cell exclusion, SRK-181 has the potential to induce tumor regression when administered in conjunction with CBT.