Comparison of Pyrrolobenzodiazepine Dimer Bis-imine versus Mono-imine: DNA Interstrand Cross-linking, Cytotoxicity, Antibody–Drug Conjugate Efficacy and Toxicity

Abstract

Antibody-drug conjugates (ADCs) delivering pyrrolobenzodiazepine (PBD) DNA crosslinkers are currently being evaluated in clinical trials with encouraging results in Hodgkin and non-Hodgkin lymphomas. The first example of an ADC delivering a PBD DNA crosslinker (loncastuximab tesirine) has been recently approved by the U.S. Food and Drug Administration for the treatment of relapsed and refractory diffuse large B-cell lymphoma. There has also been considerable interest in mono-alkylating PBD analogues. We conducted a head-to-head comparison of a conventional PBD bis-imine and a novel PBD mono-imine. Key Mitsunobu chemistry allowed clean and convenient access to the mono-imine class. Extensive DNA binding studies revealed that the mono-imine mediated a type of DNA interaction that is described as “pseudo-crosslinking,” as well as alkylation. The PBD mono-imine ADC demonstrated robust antitumor activity in mice bearing human tumor xenografts at doses threefold higher than those that were efficacious for the PBD bis-imine ADC. A single-dose toxicology study in rats demonstrated that the maximum tolerated dose of the PBD mono-alkylator ADC was approximately threefold higher than that of the ADC bearing a bis-imine payload, suggesting a comparable therapeutic index for this molecule. However, although both ADCs caused myelosuppression, renal toxicity was observed only for the bis-imine after repeated dosing, indicating possible differences in toxicological profiles that could influence tolerability and therapeutic index. These data show that mono-amine PBDs have physicochemical and pharmaco-toxicological properties distinct from their crosslinking analogues and support their potential utility as a novel class of ADC payload.

On Demand Bioorthogonal Switching of an Antibody-Conjugated SPECT Probe to a Cytotoxic Payload: from Imaging to Therapy

“…Neither ArDC nor ADC induced significant weight loss in the mice at the doses employed (Supplementary Figure 1). The attenuated potency of ArDC is consistent with that observed in previous studies of PBD dimer ADCs wherein the C11–N10 imine was oxidized or the N10 amine was irreversibly modified. ,, …”

“…The attenuated potency of ArDC is consistent with that observed in previous studies of PBD dimer ADCs wherein the C11−N10 imine was oxidized or the N10 amine was irreversibly modified. 23,30,34 We assessed next the stability of the ArDC payload, considering specifically the propensity for deconjugation from the antibody, partial hydrolysis or proteolysis of the TCO-PAB-DOTA group or isomerization of the strained TCO ring to cis-cyclooctene (CCO). Mass spectrometry of ArDC in buffer showed it to be nearly homogeneous upon preparation (Figure 3A) and storage at 4 °C for months in aqueous buffer was possible without observable degradation (data not shown).…”

Antibody–Drug Conjugates for the Treatment of Renal Cancer: A Scoping Review on Current Evidence and Clinical Perspectives

“…GS-16M8F and AGS-16C3F are two ADCs composed of fully human IgG2a conjugated to MMAF via a non-cleavable linker [ 42 , 58 ]. Their target is ectonucleotide pyrophosphatase/phosphodiesterase 3 (ENPP3: CD203a), a member of the ENPP family.…”

“…Nevertheless, the high ENPP3 expression in neoplastic cells makes it a conceivable therapeutic target [ 60 , 61 ]. In particular, it has been found in patients with ccRCC and, to a lesser extent, in patients with papillary RCC [ 58 ].…”

“…The first anti-ENPP3 mAb for the treatment of RCC was hybridoma-derived AGS-16M8F; in consideration of the high cost and long time to produce antibodies via hybridomas, a second antibody directed against ENNP3, based on the Chinese Hamster Ovary (CHO) cell line system, AGS-16C3F, was derived [ 58 ]. In 2018, the results of two sequential phase I studies were published based on the administration of these ADCs, (NCT01114230) and (NCT01672775) [ 42 ].…”