Abstract CT236: Advanced solid cancer therapy with a novel antibody-drug conjugate (ADC), sacituzumab govitecan (IMMU-132): key preclinical and clinical results
Authors: Starodub Alexander N. , Ocean Allyson J. , Bardia Aditya , Guarino Michael J. , Messersmith Wells , Berlin Jordan , Picozzi Vincent J. , Thomas Sajeve S. , Masters Gregory , Vahdat Linda T. , Mayer Ingrid A. , Moroose Rebecca , Diamond Jennifer S. , Tagawa Scott T. , Shah Manish A. , Wilhelm Francois , Wegener William A. , Maliakal Pius , Sharkey Robert M. , Goldenberg David M. 
Published: August 2015

Background: Sacituzumab govitecan (IMMU-132) is a new ADC comprising SN-38, the active metabolite of the topoisomerase inhibitor, camptothecin (irinotecan), conjugated to an anti-Trop-2 antibody. In vitro and in vivo preclinical data suggest that IMMU-132 is a unique ADC, being most efficacious at a high drug-antibody ratio (DAR) of 7.6, and capable of delivering up to 135-fold more SN-38 than its parental drug, irinotecan, in a human cancer xenograft. In vitro studies also demonstrate specific double-stranded DNA breaks by the internalizing ADC.

Methods: IMMU-132 is completing a phase I/II clinical trial with phase II expansion after MTD determination (ClinicalTrials.gov.NCT01631552) in patients with advanced cancers that typically express high levels of Trop-2, at doses of 8 and 10 mg/kg on days 1 and 8 of 21-day repeated cycles. Efficacy (N = 91) and safety (N = 130) results are provided.

Results: The% of grades 3/4 AEs for both dose levels are neutropenia (16/4), febrile neutropenia (4/4), anemia (4/0), diarrhea (4/0), and fatigue (4/0) (Table 1). No patient discontinued therapy due to toxicity, and no patient showed immunogenicity despite repeated therapy. Patient dose reductions were 15-16%, and dose delays after first 2 cycles were 3-4%.

Conclusions: IMMU-132 shows activity in patients with diverse cancers, even when they no longer responded to a topoisomerase inhibitor. It appears to have a manageable toxicity profile, with promising efficacy at a high therapeutic index in patients with heavily-pretreated metastatic cancers, especially TNBC, SCLC, and NSCLC. Based on these results, this ADC carrying a moderately-toxic drug that is the active metabolite of a currently-used camptothecin analogue represents a novel cancer therapeutic that challenges the current dogma of requiring ultratoxic drugs conjugated at low DARs for ADC therapy.

Tumor typeORR (CR+PR)Disease stabilization (CR+PR+SD)Clinical benefit (CR+PR+ SD &gt; 6 moMedian TPP (mo)TNBC (N = 31)TNBC (N = 31)23%71%39%3.7+NSCLC (N = 15)27%73%42%3.3+SCLC (N = 19)26%53%29%2.8+CRC (N = 26)4%58%24%3.7

Citation Format: Alexander N. Starodub, Allyson J. Ocean, Aditya Bardia, Michael J. Guarino, Wells Messersmith, Jordan Berlin, Vincent J. Picozzi, Sajeve S. Thomas, Gregory Masters, Linda T. Vahdat, Ingrid A. Mayer, Rebecca Moroose, Jennifer S. Diamond, Scott T. Tagawa, Manish A. Shah, Francois Wilhelm, William A. Wegener, Pius Maliakal, Robert M. Sharkey, David M. Goldenberg. Advanced solid cancer therapy with a novel antibody-drug conjugate (ADC), sacituzumab govitecan (IMMU-132): key preclinical and clinical results. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr CT236. doi:10.1158/1538-7445.AM2015-CT236