Abstract 652: Exploring the therapeutic benefit of AVA-NP-695 with combination modalities in ICB refractory and rare cancers

Abstract Background: Ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1) expression is associated with poor prognosis in many cancers. Previous studies identified ENPP1 as the primary hydrolase of extracellular cGAMP, that activates the anticancer STING pathway. High ENPP1 expression is found in several tumors, including human astrocyte tumors and triple-negative breast cancer (TNBC) cell lines, where it contributes to tumor progression and impedes T cell infiltration. By inhibiting cGAS-STING-mediated immune activation and producing adenosine, an immune suppressor that promotes cell migration, ENPP1 plays a critical role in tumor growth. Interestingly, surface and global proteome analyses identify ENPP1 as potential immunotherapeutic targets in case of rare cancers like sarcomas. Methods: The inhibition potency of AVA-NP-695 was confirmed by 5’TMP and 2’2’-cGAMP enzymatic assays. Pharmacokinetic profile of AVA-NP-695 in Mice, Rats and Beagle Dogs and the human PK profile was predicted. The efficacy of AVA-NP-695 was demonstrated in 4T1 Tumor bearing BALB/c mice as monotherapy and in combination with anti-PD-L1, Olaparib and Paclitaxel. Finally, in vivo the effect of pharmacological inhibition of DDR with Olaparib in combination with AVA-NP-695 was assessed in OS models. Results: We demonstrate that AVA-NP-695, a selective and potent small molecule ENPP1 inhibitor, exhibited no adverse effects in multiple safety studies in mice and beagle dogs. In vivo studies revealed that AVA-NP-695 (6 mg/kg BID) provided superior tumor growth inhibition and reduced metastasis compared to Olaparib and Anti-PD1 in a syngeneic 4T1 breast cancer mouse model. Additionally, AVA-NP-695 demonstrates tumor regression in both paratibial (OT) and metastatic (lung) models of Osteosarcoma (OS). AVA-NP-695 significant increase the cGAMP levels (∼2-3 fold) as early as 6h post-treatment, without additional stimulation. A targeted pharmacological screen revealed synthetic lethality when combining AVA-NP-695 with Olaparib (PARPi) in vitro OS cell lines. This novel combination increased both intra- and extracellular cGAMP production. Additionally, the pharmacological inhibition of DDR with Olaparib in combination with AVA-NP-695 led to OS tumor regression and enhanced antitumor immune responses in both OT and metastatic contexts. Compassionate use of AVA-NP-695 showed > 80% tumor volume reduction in Canine patients. Conclusions: The potent anti-tumor efficacy of AVA-NP-695 both as monotherapy and combination along with its safety profile provides a strong rationale for the therapeutic potential of AVA-NP-695 against solids tumors (breast cancer and Osteosarcoma). Our results uncover novel mechanistic vulnerabilities and suggest that treatment with AVA-NP-695 in combination may increase effectiveness in patients, thus preventing local and distant dissemination. Citation Format: Borja Ruiz-Fernandez de Cordoba, Avijit Goswami, Sandeep Goyal, Kawaljit Singh, Princy Khurana, Alejandro Sweet-Cordero, Aditya Kulkarni. Exploring the therapeutic benefit of AVA-NP-695 with combination modalities in ICB refractory and rare cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 652.