-- New development candidate, NTX-452, a non-covalent WRN inhibitor, demonstrated significant tumor regression and complete responses at low oral doses in MSI-H tumor models refractory to immunotherapy and chemotherapy --

-- Company plans to initiate clinical trial of NTX-452 in first half of 2025 --

Nimbus Therapeutics, LLC ("Nimbus Therapeutics" or "Nimbus"), a biotechnology company that designs and develops breakthrough medicines for patients through its powerful computational drug discovery engine, announced that it is presenting preclinical data on its new development candidate, NTX-452, a novel Werner syndrome helicase (WRN) inhibitor, at the 36^th EORTC-NCI-AACR Symposium on Molecular Targets and Cancer Therapeutics, taking place October 23-25, 2024 in Barcelona, Spain.

WRN is a helicase required for DNA replication and DNA repair and is a validated target for tumors with microsatellite instability (MSI). MSI is a phenotypic consequence of defective mismatch repair (dMMR) and occurs in various tumor types, including colorectal, gastric and endometrial cancers. Inhibition of WRN activity has the potential to induce synthetic lethality in MSI-high (MSI-H) tumors. Using a structure-based drug design approach, Nimbus developed highly potent and selective covalent and non-covalent inhibitors of WRN, and has selected a novel non-covalent inhibitor, NTX-452, as the clinical candidate.

In a poster (abstract #356) titled "Preclinical Characterization of NTX-452, a Potent, Selective and Highly Efficacious WRN Inhibitor for the Treatment of MSI-H Tumors," Nimbus is presenting new data from preclinical assays and several tumor models that support the potential of the company’s non-covalent WRN inhibitor as a treatment for MSI-H tumors.

Key findings from the preclinical studies include:

• NTX-452 demonstrated potent and selective inhibition of WRN activity with favorable drug-like properties.
• The compound showed synthetic lethality in MSI-H tumor cells, triggering a DNA damage response that suppressed cell viability and promoted cell death.
• Treatment with NTX-452 at low doses in vivo exhibited a robust pharmacodynamic response, resulting in tumor regression across multiple MSI-H cell line-derived xenograft (CDX) and patient-derived xenograft (PDX) tumor models, including established models for colorectal, gastric and endometrial cancers.
• Significant tumor regression and complete responses were observed at low oral doses in MSI-H models refractory to immunotherapy and chemotherapy.

"These compelling preclinical results for NTX-452 further highlight the significant potential of our WRN inhibitor as a promising therapeutic approach for patients with MSI-H tumors, many of whom fail to respond to or eventually relapse with current standard of care therapies including immune checkpoint inhibitors," said Peter Tummino, Ph.D., Chief Scientific Officer of Nimbus. "Our novel non-covalent approach to WRN inhibition, coupled with the robust efficacy demonstrated across diverse tumor types and treatment settings, positions our program for potential best-in-class status. We are particularly encouraged by the low doses required to achieve robust anti-tumor activity in preclinical models, which may translate to an improved benefit-risk profile in the clinic."

The preclinical profile of NTX-452 suggests several potential advantages in the treatment of MSI-H tumors, including:

• The non-covalent mechanism may offer more durable on-target activity, and a greater safety window compared to covalent inhibitors.
• High potency and favorable pharmacokinetic properties indicate the potential for target levels of efficacy at lower doses.
• Broad efficacy across treatment-naïve, chemotherapy-pretreated, and immunotherapy-pretreated models suggests potential utility in both early-stage and advanced disease settings.
• Activity in multiple MSI-H tumor types, including those with diverse genetic alterations, indicates potential broad applicability across dMMR/MSI-H cancers.

Nimbus is advancing NTX-452 with plans to enter the clinic in the first half of 2025.

About Nimbus Therapeutics

Nimbus Therapeutics is a clinical-stage, structure-based drug discovery company developing novel small molecule medicines designed to act against well-validated but difficult-to-drug targets implicated in multiple human diseases. The company advances promising research based on a unique strategy that combines leading-edge computational technologies with a tailored array of machine learning-based predictive modeling approaches. Nimbus' pipeline includes a clinical-stage HPK1 inhibitor for the treatment of cancer (NCT05128487), as well as a diverse portfolio of preclinical programs focused on cancer, including the WRN program, autoimmune conditions, and metabolic diseases. The company is headquartered in Boston, Mass. To learn more about Nimbus, please visit www.nimbustx.com.

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