Ribon Therapeutics Announces Oral Presentation of Positive Interim Data from Phase 1 Trial of RBN-2397 in Patients with Advanced Solid Tumors at 2021 ASCO Annual Meeting

– RBN-2397 was well tolerated and demonstrated evidence of target inhibition and preliminary signs of clinical activity

– One partial response (PR) and nine patients with stable disease (SD) > 4 months in a heavily pretreated, heterogenous patient population

CAMBRIDGE, Mass.–(BUSINESS WIRE)–Ribon Therapeutics, a clinical stage biotechnology company developing therapeutics targeting stress support pathways, announced positive interim clinical data from the dose escalation portion of its first-in-human Phase 1 trial evaluating RBN-2397, a small molecule inhibitor of PARP7, as a monotherapy in patients with advanced solid tumors. Presenting the data in an oral presentation at the American Society of Clinical Oncology (ASCO) Annual Meeting on June 4, 2021, will be Gerald S. Falchook, M.D., Director, Drug Development, Sarah Cannon Research Institute at HealthONE, Denver, CO and Clinical Investigator in the RBN-2397 Phase 1 trial.

“We are pleased to see demonstration of target inhibition and preliminary signs of antitumor activity in this early stage of clinical development of a novel target,” said Dr. Falchook. “In the expansion part of the study, we will seek to demonstrate definitive clinical activity in tumor types predicted to respond to RBN-2397.”

The primary objectives of the study are to determine any dose limiting toxicities (DLTs), maximum tolerated dose (MTD), and establish the recommended phase 2 dose (RP2D). The dose escalation portion evaluated two dosing schedules with multiple ascending dose cohorts of RBN-2397. As of April 1, 2021, the dose escalation portion of the study, in which 50 patients were enrolled, is complete and the key results are as follows:

• Single-agent RBN-2397 was well-tolerated at exposures predicted to be efficacious in preclinical studies
• RP2D was 200 mg BID on a continuous dosing schedule
• In this heavily pretreated, heterogenous patient population, preliminary antitumor activity was observed with one partial response (PR) in a patient with HR+ breast cancer and nine patients with stable disease (SD) > 4 months
  • Includes one patient with squamous cell carcinoma of lung (SCCL) who has been on study with SD for 17+ months and 29% tumor shrinkage post data cutoff date and a second SCCL patient with SD for 4+ months and 19% tumor shrinkage
• Proof of mechanism demonstrated by increase in tumoral Type I interferon (IFN) response and immune cells after treatment with RBN-2397
• Expansion phase is currently enrolling patients in a number of defined cohorts, including SCCL

“These results validate our approach to drug development by targeting cellular stress and modulating the immune system to induce antitumor activity,” said Sudha Parasuraman, M.D., Chief Medical Officer, Ribon Therapeutics. “We expect the expansion part of the study to establish proof of concept for RBN-2397 monotherapy and look forward to expanding our development program with the initiation of a Phase 1b/2 combination study with pembrolizumab in SCCL in the second half of 2021.”

At the conclusion of the ASCO Annual Meeting, a copy of the presentation will be available on the Ribon Therapeutics site at https://ribontx.com/publications/.

About RBN-2397

RBN-2397 is an orally available small molecule inhibitor of PARP7 that Ribon Therapeutics is developing for the treatment of solid tumors. PARP7 is upregulated in response to cellular stress, including genomic instability in cancers, and acts as a brake on the cellular stress response by negatively regulating the Type I interferon response. By inhibiting PARP7 in tumor cells, RBN-2397 has been shown to directly inhibit cellular proliferation and restore interferon signaling to stimulate an innate and adaptive antitumor immune response. RBN-2397 is currently in a Phase 1 clinical trial as a monotherapy in patients with advanced solid tumors (NCT04053673). PARP7 is overexpressed in a number of tumors, including squamous cell carcinoma of the lung, or SCCL, which represents approximately 30% of all non-small cell lung cancers.

About Ribon Therapeutics

Ribon Therapeutics is a clinical stage biotechnology company developing therapeutics targeting novel enzyme families activated under cellular stress conditions that contribute to disease. We are exploring novel areas of biology to develop effective treatments for patients with limited therapeutic options. Leveraging our proprietary BEACON⁺ (Blocking the Enzyme Activity Component of NAD⁺) platform, we are building a pipeline of selective, small molecule inhibitors to numerous NAD⁺-utilizing enzymes, beginning with monoPARPs, which have applications across multiple therapeutic areas. Our lead program is RBN-2397, a PARP7 inhibitor in clinical development for the treatment of cancer. Ribon is located in Cambridge, Massachusetts. For more information visit www.RibonTx.com.

Contacts

Brendan Burns

Argot Partners

212.600.1902

[email protected]