Abstract P5-05-04: Inhibition of HER2+ tumor growth with SDX-7320, a novel MetAP2 inhibitor, alone and in combination with capivasertib/AZD-5363: Reduced expression of hypoxia-inducible and innate-immune system genes

Abstract MetAP2 inhibitors have shown clinical anti-tumor activity, but CNS side effects and poor drug-like properties have generally limited their development. SDX-7320 is a polymer-drug conjugate of a novel fumagillin-derived MetAP2 inhibitor (SDX-7539) attached via a cleavable linker to a hydroxypropylmethacrylamide (HPMA) polymer backbone. This conjugation approach is intended to improve safety (i.e., limit CNS penetration) while also improving biodistribution and pharmacokinetics relative to small molecule MetAP2 inhibitors. SDX-7320 recently completed a phase I safety trial in late-stage cancer patients (NCT02743637) and was well-tolerated with no apparent CNS side effects. In prior models of breast cancer, SDX-7320 significantly inhibited the growth of syngeneic EO771 triple-negative breast cancers (TNBC) accelerated by obesity/metabolic dysfunction (i.e., “metabo-oncology”) and also synergized with the PI3Kα inhibitor alpelisib/Piqray® in ER+/Her2- MCF-7 xenografts. The objectives of these experiments were to determine the effect of SDX-7320 on the growth of Her2+ xenografts alone or in combination with the Akt/mTOR inhibitor capivasertib/AZD-5363 and to determine if SDX-7320 could attenuate hyperglycemia induced by capivasertib/AZD-5363. Female athymic, nude mice (9 weeks of age) were surgically implanted with slow-release estrogen pellets (90-day, 0.72 mg, inter-scapular) and three days later 2 x 107 BT474 cells (in Matrigel/RPMI-1640, 50/50, v/v) were injected into the fourth mammary gland. When the group mean tumor volume exceeded 100 mm3, treatment with test agents commenced. SDX-7320 (sc/q4d, 6, 12 mg/kg) exerted significant, dose-dependent inhibition of BT-474 tumor growth (TGI of 61 and 88% respectively), whereas capivasertib/AZD-5363 (po, qd, 100, 200 mg/kg) exhibited significant anti-tumor activity only at 200 mg/kg (54% TGI). The combination of SDX-7320 (12 mg/kg) plus capivasertib/AZD-5363 (200 mg/kg) produced additive effects in that a greater number of mice had tumor regression relative to mice treated with either SDX-7320 or capivasertib/AZD-5363 alone. Tumor tissue from a subset of treatment groups (Vehicle, SDX-7320-12 mg/kg, SDX-7320-12 mg/kg + AZD-5363-200 mg/kg, and AZD-5363-200 mg/kg) was snap frozen and stored at -80oC. PolyA+ RNA was isolated, cDNA libraries were constructed and RNASeq was conducted (range of 20-30 reads per million (RPM) base pairs). Analysis of RNASeq data showed that SDX-7320 alone significantly attenuated the expression of hypoxia-induced genes as well as genes related to the innate immune system. Based on these results, we conclude that SDX-7320 affected tumor growth by limiting the ability of tumors to adapt to a hypoxic microenvironment and by altering the innate tumor-immune microenvironment. In normal male, C57Bl/6 mice, capivasertib/AZD-5363 (200 mg/kg, po) elevated blood glucose after a single dose. Pretreatment with either one dose (24 hours before the Akt/mTOR inhibitor) or multiple doses (Q4D beginning 14 days prior to Akt/mTOR inhibitor) of SDX-7320 (8 mg/kg) significantly inhibited hyperglycemia induced by capivasertib/AZD-5363. In summary SDX-7320 significantly inhibited the growth of BT-474 xenografts, alone and in combination with capivasertib/AZD-5363, which was associated with suppression of hypoxia-induced genes, as well as genes of the innate immune system. In addition, SDX-7320 improved the safety profile of capivasertib/AZD-5363 by attenuating Akt/mTOR inhibitor-induced hyperglycemia, providing further support for the clinical exploration of SDX-7320 in combination with Akt/mTOR inhibitors in Her2+ breast cancer. Citation Format: Peter Cornelius, Benjamin Mayes, Pierre Dufour, Mark Kalinich, Jonathan Wang, Sara Little, Bradley Carver, James Shanahan. Inhibition of HER2+ tumor growth with SDX-7320, a novel MetAP2 inhibitor, alone and in combination with capivasertib/AZD-5363: Reduced expression of hypoxia-inducible and innate-immune system genes [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P5-05-04.