Abstract CT153: SDX-7320 elicits improvements in tumor-related and metabolic biomarkers: Results of a phase 1 dose-escalation study in patients with advanced refractory or late-stage solid tumors

Background and Rationale: Metabo-oncology is the study of specific tumor types whose growth and/or metastasis is accelerated by metabolic dysfunction, often associated with hyper-adiposity. In this setting the metabolic hormones leptin, adiponectin and insulin are potential mediators. SDX-7320 is a novel methionine aminopeptidase type 2 inhibitor (MetAP2) being developed for use in combination with other anti-cancer agents to treat the metabo-oncology patient population.

Study Design: This first-in-human study used a 3+3 design with dose expansion at the RP2D. Measurements included standard assessments of safety, tolerability, as well as inhibition of MetAP2 in whole blood, plasma levels of protein biomarkers and drug exposure. Tumor response was measured using RECIST v.1.1.

Results: 32 patients with an average of 5.3 prior treatment regimens were dosed. Sub-cutaneous dosing of SDX-7320 began at 1.7 mg/m2 once per week (Q7D, 28 days/cycle) and was escalated to 49 mg/m2. Repeated Q7D administration at 49 mg/m2 resulted in dose-limiting (G3-G4) thrombocytopenia. Expansion at 49 mg/m2 confirmed thrombocytopenia as the dose-limiting toxicity (DLT), reversible upon cessation of dosing. Dose-escalation was re-initiated at 36 mg/m2 every two weeks (Q14D). Repeated dosing at 65 mg/m2 (Q14D) resulted in G3 reversible thrombocytopenia. Expansion at 49 mg/m2 (Q14D) confirmed that this was the maximum tolerated dose (MTD) on a Q14D schedule. No deaths or Grade 5 TEAEs attributable to SDX-7320 were reported. Six patients had a combined total of 9 Grade 3/4 TEAEs considered by the Investigator to be at least possibly SDX-7320-related: thrombocytopenia (4 patients) and single cases of anemia, anorexia, fatigue, QTc prolonged, and vasculitis. Fourteen patients (44% had stable disease &gt2 cycles and three patients had stable disease for ≥6 cycles. Inhibition of MetAP2 in whole blood was 100% at all doses evaluated while the time to reach 100% inhibition was inversely related to dose. When stratified for elevated baseline levels, the following biomarkers declined after initiating SDX-7320 (average of each patient's maximum % change relative to baseline +/- SD): bFGF (-53 +/- 76%), VEGF-C (-35 +/- 39%), and insulin (-55 +/- 30%). Without stratification, leptin levels declined (-51 +/-29%) and levels of adiponectin increased after SDX-7320 (+74 +/- 63% relative to baseline).

Conclusions and Next Steps : SDX-7320 was well-tolerated with prolonged stable disease in an open-label, phase I first-in-human study. Improvements were observed in both tumor-related and metabolic biomarkers. Additional studies of SDX-7320 (in combination with other anti-cancer agents) in patients with solid tumors sensitive to metabolic hormones are scheduled. SDX-7320 is the first novel agent in clinical development to treat the metabo-oncology patient population.

Citation Format: Monica M. Mita, Johanna Bendell, Alain C. Mita, Michael Gordon, Jasgit Sachdev, Bradley J. Carver, James Shanahan, Benjamin Mayes, Kris Awerkamp, David Browning, Neal Salomon, Kimberly Sullivan, Alfred Anderson-Villaluz, Joe Johnson, John S. Petersen, David J. Turnquist, Peter Cornelius. SDX-7320 elicits improvements in tumor-related and metabolic biomarkers: Results of a phase 1 dose-escalation study in patients with advanced refractory or late-stage solid tumors [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr CT153.

Abstract 4919: Preclinical activity of SDX-7320 in mouse models of obesity and obesity-driven cancer

Cancer patients who are obese face a greater risk of dying from cancer compared to nonobese patients (Calle, 2003). Obesity is believed to contribute to metastasis and progression of cancer via multiple mechanisms: increased secretion of the adipose tissue hormone leptin, decreased secretion of adiponectin, increased production of estrogen in adipose tissue, and elevated insulin (secondary to peripheral insulin resistance) as well as the local effects of inflammatory cytokines (Gucalp, 2016). Small-molecule inhibitors of methionine aminopeptidase type 2 (MetAP2) have previously demonstrated clinical activity in oncology (Kudelka, 1998) as well as obesity/type 2 diabetes (Hughes, 2013; Kim, 2015). However, development of some small-molecule MetAP2 inhibitors has been hampered by CNS side effects (Bhargava, 1999). SDX-7320 is a copolymer-drug conjugate of a novel fumagillin-derived MetAP2 inhibitor (SDX-7539) attached via a cleavable linker to a hydroxypropylmethacrylamide (HPMA) backbone, intended to limit CNS penetration and therefore reduce CNS toxicity. In vitro MetAP2 binding assays showed that SDX-7320 was unable to bind to MetAP2 while SDX-7539 was a potent binder (apparent IC50 = 0.13 nM), indicating that cleavage of SDX-7320 is required for biologic activity. SDX-7539 inhibited proliferation of human umbilical vein endothelial cells (HUVECs) with an apparent IC50 = 0.2 nM. The preclinical efficacy of SDX-7320 was evaluated in mouse models of obesity/insulin resistance and also in syngeneic tumor models coupled with high fat diet-induced obesity (DIO)/metabolic dysfunction. Obesity and insulin resistance were induced in C57Bl/6 mice by feeding them a high-fat diet (HFD) for at least 12 weeks. SDX-7320 was dosed subcutaneously every 4 days (for 28 days) into DIO mice or control mice fed a low-fat diet. SDX-7320 caused significant reduction in body weight and fat mass in obese mice while also reversing insulin resistance relative to controls. In addition, SDX-7320 caused greater reduction in body weight in obese mice relative to lean mice. Circulating levels of leptin and insulin were reduced while levels of adiponectin were increased in response to SDX-7320. In mouse models of obesity-accelerated tumor growth, SDX-7320 was more efficacious in obese relative to lean mice harboring subcutaneous B16F10 melanoma or EO771 mammary gland tumors. These effects occurred without any signs of neurotoxicity. SDX-7320, currently in phase I (solid tumors; all-comers; NCT02743637), is being developed for the treatment of cancers whose progression is accelerated in the setting of obesity and host metabolic dysfunction, termed “metabo-oncology.”

Citation Format: Peter Cornelius, John S. Petersen, Benjamin Mayes, David Turnquist, Kimberly Sullivan, Alfred Anderson-Villaluz, Robert Lutz, Sara Little, Andrew Slee, Bradley J. Carver, James Shanahan. Preclinical activity of SDX-7320 in mouse models of obesity and obesity-driven cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4919.

Abstract 5483: Preclinical evaluation of IMGN289, an anti-EGFR antibody-maytansinoid conjugate for the treatment of squamous cell carcinoma of the head and neck

Squamous cell carcinoma of the head and neck (SCCHN) include cancers that affect the squamous epithelium of the mouth, larynx, nasal passages, sinuses and pharynx. The epidermal growth factor receptor (EGFR) has emerged as an important antigen for novel targeted therapies in SCCHN, where EGFR overexpression correlates with aggressive disease, resistance to standard therapies and a poor prognosis.

EGFR expression was evaluated on a panel of SCCHN xenografts and primary SCCHN tumors using a calibrated immunohistochemical (IHC) staining method on formalin-fixed paraffin-embedded sections. The results demonstrated that 83 of 85 (98%) SCCHN tumors stained positive for EGFR and, of the 83 positive tumors, 80 (96%) had high EGFR expression, confirming that EGFR represents an attractive therapeutic target for SCCHN.

IMGN289 is an antibody-“drug” conjugate (ADC) consisting of the humanized monoclonal antibody, J2898A, which selectively binds to EGFR, linked to the potent cytotoxic maytansinoid, DM1, via a SMCC thioether linker. The cytotoxic activity of IMGN289 was evaluated against a panel of SCCHN cell lines in vitro. IMGN289 was active in 9 of 13 cell lines assayed, including 5 of 8 that were resistant to cetuximab. Cytotoxic activity was observed against cell lines originating from multiple anatomic sites including the pharynx, oral cavity, larynx and tongue.

The anti-tumor activity of IMGN289 was evaluated in EGFR-positive SCCHN xenograft models with expression levels comparable to patient tumors. Immunodeficient mice bearing established subcutaneous xenograft tumors were treated with a single intravenous injection of IMGN289 at 1, 2.5 or 5.0 mg/kg (based on antibody concentration). A group of mice dosed with the J2898A antibody at 5 mg/kg was included in the study. In the FaDu xenograft model, IMGN289 was active with a minimally efficacious dose (MED) of 1 mg/kg, highly active at 2.5, and at 5 mg/kg 5/6 partial regressions (PR) and 2/6 complete regressions (CR) were observed. Conjugation of DM1 to J2898A achieved greater anti-tumor activity than J2898A, which was active in the study but without regressions. In the HSC-2 xenograft model, IMGN289 was also highly active, with a MED of 2.5 mg/kg and tumor regression at 5 mg/kg with 6/6 PR and 4/6 CR. Once again, the activity of IMGN289 was more robust than naked J2898A antibody, which was active with 2/6 PR and 1/6 CR.

The strong anti-tumor activity of IMGN289 against SCCHN xenograft tumors with EGFR expression levels comparable to patient tumors suggests that IMGN289 may be a promising compound for the treatment of SCCHN.

Citation Format: Jose F. Ponte, Yulius Y. Setiady, Ling Dong, Anna Skaletskaya, Christina N. Carrigan, Alfred Anderson-Villaluz, Robert J. Lutz, Jan Pinkas. Preclinical evaluation of IMGN289, an anti-EGFR antibody-maytansinoid conjugate for the treatment of squamous cell carcinoma of the head and neck. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5483. doi:10.1158/1538-7445.AM2013-5483