TNG348

This inhibitory effect translates into in vitro cellular viability defects in a BRCA1-mutant breast cancer cell line, as well as an in vivo pharmacodynamic (PD) response and tumor growth suppression in a mouse xenograft efficacy model. Additionally, we report an X-ray co-crystal structure of TNG-6132 (18) bound in the USP1-UAF1 complex, a result that furthered our understanding of the role played by key elements of the pharmacophore of this chemotype as well as its mechanism of inhibition of USP1.

Importantly, our data in human cancer models further show that the addition of TNG348 to PARPi treatment can overcome acquired PARPi resistance in vivo. While the clinical development of TNG348 has been discontinued due to unexpected liver toxicity in patients (NCT06065059), the present data provides preclinical and mechanistic support for the continued exploration of USP1 as a drug target for the treatment of patients with BRCA1/2 mutant or HRD cancers.

P1/2, N=7, Terminated, Tango Therapeutics, Inc. | N=140 --> 7 | Trial completion date: Jun 2026 --> May 2024 | Recruiting --> Terminated | Trial primary completion date: Dec 2025 --> May 2024; Terminated due to safety

P1/2, N=140, Recruiting, Tango Therapeutics, Inc. | Not yet recruiting --> Recruiting

P1/2, N=140, Not yet recruiting, Tango Therapeutics, Inc.

Furthermore, TNG348 activity extends beyond BRCA1/2mut models with PARP inhibitor (PARPi) sensitivity and oncogene-induced replication stress being additional features correlating with USP1 inhibitor sensitivity based on cell line panel and CRISPR screening results. We show that TNG348 induces cell death through a pathway that is distinct from PARPi and TNG348 demonstrates robust synergy when combined with first- or second-generation PARPi. The clinical development plan intends to evaluate TNG348 in patients with BRCA1/2 mutations as single agent and in combination with PARP1i in patients naïve to PARPi and with prior PARPi treatment history.

Strong in vivo anti-tumor activity across multiple tumor models was demonstrated with USP1 inhibition alone and in combination with the PARP1 inhibitor olaparib. Our studies suggest that USP1 and PARP1 inhibitors target BRCA1-mutant cancer though distinct yet synergistic mechanisms. As such, USP1 inhibitors may provide novel treatment strategies for PARP1 inhibitor-resistant and -naïve BRCA1-mutant cancer.