Abstract 2794: A Quantitative Systems Pharmacology (QSP) model to characterize dose-dependent antitumor activity of AZD5305, PARP1 selective inhibitor, across multiple xenograft models
Authors: Moorthy Ganesh , Voronova Veronika , Pichardo Cesar , Peskov Kirill , Illuzzi Giuditta , Staniszewska Anna , Albertella Mark , Kimko Holly 
Published: April 2023

Abstract
AZD5305 is a potent and selective PARP1 inhibitor and trapper which is hypothesized to improve therapeutic index over first generation nonselective PARP inhibitors. AZD5305 demonstrated significant and sustained antitumor activity in multiple BRCA1/2 mutant xenograft models. Here we present a mechanistic Quantitative Systems Pharmacology (QSP) model to analyze dose-dependent antitumor activity of AZD5305 (0.01-10 mg/kg) across a selection of xenograft models with different homologous recombination repair (HRR) status (Capan-1, DLD-1 BRCA2 KO, HBCx-9, HBCx-17, MDA-MB-436 and SUM149PT). A QSP model was developed based on a system of ordinary differential equations (ODEs) to address formation and repair of trapped PARP-DNA fragments and longitudinal changes in tumor size as a function of pharmacokinetic (PK) profiles in individual animals. Tumor growth data as well as intratumoral PARylation inhibition from xenograft models were utilized for model development and qualification. Model parameters characterizing intrinsic tumor growth and cancer cell sensitivity to accumulated DNA damage, were set to be different across xenograft models, to provide unbiased data reproduction. Sensitivity analyses were performed to identify model parameters which have the most impact on differential antitumor activity observed across various xenograft models. Maximal antitumor efficacy was seen at 0.1 to 1 mg/kg AZD5305, depending on the tumor model. Exposures at 1 mg/kg were similar to those causing peak PARP1 trapping in vitro. The QSP model adequately captures antitumor activity across different xenograft models. Simulations indicate antitumor activity of AZD5305 was driven mainly by differences in the HRR status-related model parameter (khrr). Xenograft models with HRR deficiency such as HBCx-17, DLD-1 BRCA2 KO and MDA-MB-436 (with a very low khrr) were the most sensitive to AZD5305 and treatment led to tumor regressions. In contrast, tumor models with partial sensitivity, such as HBCx-9, Capan-1, SUM149PT (with khrr up to 1000-fold higher than in the sensitive tumors), AZD5305 only achieved tumor growth inhibition. Dosing AZD5305 at 0.03 mg/kg daily was associated with tumor regression in HBCx-17 and MDA-MB-436 xenografts, whereas 1 mg/kg daily dosing was required to achieve tumor regression in the DLD-1 BRCA2 KO model, and maximal tumor growth inhibition in less sensitive models. Further biomarker analyses to assess functional HRR status (e.g. via RAD51 foci score) in these xenograft models is ongoing to validate model estimated khrr parameters. The calibrated model was used to predict antitumor activity of AZD5305 at clinically relevant exposures observed in the phase I clinical study PETRA. Model-based simulations indicated near maximal efficacy at clinical doses equivalent to 1 mg/kg AZD5305 exposure in xenograft models.
Citation Format: Ganesh Moorthy, Veronika Voronova, Cesar Pichardo, Kirill Peskov, Giuditta Illuzzi, Anna Staniszewska, Mark Albertella, Holly Kimko. A Quantitative Systems Pharmacology (QSP) model to characterize dose-dependent antitumor activity of AZD5305, PARP1 selective inhibitor, across multiple xenograft models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2794.