SG 2000

All the pyrrolobenzodiazepines tested - SJG136, SGD-1882, SG2057, and SG3199 - were substrates of P-gp, ABCG2, and MRP1. The modified anthracyclines nemorubicin and its metabolite PNU-159682 were poorly transported by both ABCB1 and ABCG2 and displayed nanomolar to picomolar toxicity. Further, we found that the efficacy of the recently FDA-approved ADC mirvetuximab soravtansine, which has DM4 as the toxic payload, was decreased in cell lines with overexpression of P-gp. Several commonly used ADC payloads can be effluxed from cells by ABC transporters which may lead to transporter-mediated drug resistance in patients. Future ADCs should be developed using payloads that are not substrates of ABC transporters.

ADCT-212 was tolerated as a single 20 mg/kg dose in male rats, with exposure data being indicative of a linear PK profile with a half-life of approximately 12 days. In conclusion, ADCT-212 demonstrated potent and specific in vitro and in vivo anti-tumor activity while it was stable and well tolerated in the rat, warranting further development of ADCT-212 into the clinic.

ADCT-211 is an antibody-drug conjugate composed of HuCl47, a humanized IgG1 antibody directed against human IL13RA2, site-specifically conjugated using GlycoConnectTM technology to PL1801, which contains HydraspaceTM, a valine-alanine cleavable linker and the PBD dimer cytotoxin SG2000 (drug to antibody ratio ~ 1.8). Expression of membranous IL13RA2 was confirmed by IHC in a panel of primary and refractory GBM samples and malignant melanoma, highlighting them as potential indications for the clinical development of ADCT-211. In conclusion, ADCT-211 demonstrated potent and specific in vitro and in vivo anti-tumor activity and it was stable and well tolerated in the rat, warranting further development of ADCT-211 into the clinic in IL13RA2-expressing cancers.