IDRx Announces $120 Million Series B Financing to Advance Potential Best-in-class New Treatment for Gastrointestinal Stromal Tumor (GIST)

• Financing led by RA Capital Management, Commodore Capital, and Blackstone Multi-Asset Investing with participation from additional new and existing investors
• Proceeds to support ongoing Phase 1/1b StrateGIST 1 study and expected initiation of first pivotal study of IDRX-42 in second-line GIST in 2025
• IDRX-42 recently granted Fast Track designation by U.S. FDA

IDRx, Inc., a clinical-stage biopharmaceutical company dedicated to transforming cancer treatment with purpose-built precision therapies, today announced the completion of an oversubscribed $120 million Series B Preferred Stock financing. The financing was led by RA Capital Management, Commodore Capital, and Blackstone Multi-Asset Investing with additional new investors, including Rock Springs Capital and a U.S.-based healthcare-focused fund. Existing investors, including Andreessen Horowitz (a16z) Bio + Health, Casdin Capital, Nextech Invest Ltd. (on behalf of one or more funds managed by it), Forge Life Science Partners, co-founder Nick Lydon, Ph.D., and strategic partner Merck KGaA, Darmstadt, Germany also participated in the financing. Derek DiRocco, Ph.D., Partner at RA Capital Management, has joined the IDRx Board of Directors.

IDRx plans to use the proceeds from the financing to support the ongoing Phase 1/1b StrateGIST 1 study of its lead product candidate IDRX-42, a potent, oral, highly selective KIT inhibitor targeting all major categories of activating and resistance mutations in patients with KIT-mutant GIST. Additionally, proceeds will be used to fund the expected initiation of the first pivotal study for IDRX-42 in patients with second-line GIST.

At the 2024 American Society of Clinical Oncology (ASCO) annual meeting, IDRx presented preliminary Phase 1 data from the ongoing Phase 1/1b StrateGIST 1 trial. The data support the best-in-class potential of IDRX-42 in patients with GIST. This included a 23% objective response rate (ORR) across all patients (median four prior lines of therapy) and a 43% ORR in second-line patients, including those with either or both ATP binding site and activation loop mutations, with a favorable tolerability profile consistent with use in front-line and second-line settings. IDRx is now enrolling patients in the Phase 1b portion of the trial. In addition, the U.S. Food and Drug Administration (FDA) has recently granted Fast Track designation to IDRX-42 for the treatment of GIST after disease progression on or intolerance to imatinib.

“We are thrilled to announce this financing, which includes support from a top-tier syndicate of investors and positions us to accelerate the development of IDRX-42 for a broad population of patients with GIST, including in the second-line and front-line settings, where patients haven’t seen a new treatment option in over 15 years,” said Tim Clackson, Ph.D., Chief Executive Officer of IDRx. “IDRX-42 was designed to overcome the twin challenges of on-target treatment resistance and off-target driven adverse events, which limit the clinical benefit of currently available TKIs. We are extremely encouraged by the clinical data generated with IDRX-42 to date and are focused on rapidly advancing this potential new treatment option that could elevate the standard of care for GIST patients.”

“RA Capital Management is excited to co-lead this round to support the advancement of IDRX-42 as a differentiated new treatment for GIST,” said Derek DiRocco, Ph.D., Partner of RA Capital Management and board member of IDRx. “We have been extremely impressed by what the IDRx team has accomplished in a short time, and I look forward to contributing to IDRx’s future growth and success as the company prepares to execute on its late-stage clinical development activities for IDRX-42.”

About GIST

GIST is the most common subtype of soft tissue sarcoma. Approximately 80% of cases arise from gain of function mutations in the KIT receptor tyrosine kinase, driving the malignancy through constitutive activation of aberrant signaling. Resistance mutations in KIT emerge in ~90% of patients treated with imatinib, the current standard of care for GIST. In unresectable or metastatic GIST, clinical benefits from existing treatments can vary by mutation type.

About the StrateGIST 1 Study

StrateGIST 1 is an ongoing, open-label, first-in-human Phase 1/1b study designed to evaluate the safety, tolerability, pharmacokinetics, and preliminary antitumor activity of IDRX-42 in patients with metastatic and/or surgically unresectable GIST after failure of imatinib and other approved drugs. The study is currently enrolling patients with documented pathogenic mutation in KIT or any platelet-derived growth factor receptor alpha (PDGFRA) mutation (other than PDGFRA exon 18) at sites in the U.S., United Kingdom, Belgium, The Netherlands, France, Germany, Italy, Spain, and South Korea. The Phase 1b portion has been initiated and includes four expanded exploratory cohorts based on defined lines of prior TKI therapy, including front line, second line, third line + (with standard approved TKIs only), and third line + (including investigational TKIs).

About IDRX-42

IDRX-42 is a potent, oral, highly selective KIT inhibitor targeting all major categories of activating and resistance mutations in patients with KIT-mutant GIST (including variants in exons 9, 11, 13 and 17). In preclinical studies, IDRX-42 demonstrated superior antitumor activity compared to imatinib, the current first-line of therapy, in GIST human xenograft models expressing mutations in KIT exons 9 and 11. In xenograft models expressing secondary resistance mutations in KIT exon 13 or 17, IDRX-42 treatment resulted in potent and dose-dependent antitumor activity superior to the second-line standard of care agent, sunitinib. IDRX-42 is currently being evaluated in StrateGIST 1, a first-in-human Phase 1/1b study. IDRX-42 was granted Orphan Drug designation by the FDA for the treatment of GIST.

About IDRx

IDRx is a clinical-stage biopharmaceutical company dedicated to transforming cancer care with intelligently designed precision therapies. IDRx aims to address the limitations of today’s precision cancer medicines with highly potent and selective targeted therapies to stop key tumor escape mechanisms and prolong response to therapy. IDRx’s lead program is IDRX-42, designed to inhibit key genetic drivers and drug-resistant mutations of KIT in GIST. Founded in 2021, IDRx’s leadership team has extensive experience in drug development and collectively has been involved in the discovery, development, and commercialization of more than 10 approved medicines. To learn more, please visit www.idrx.com and follow us on LinkedIn.

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