Dolaflexin: A Novel Antibody–Drug Conjugate Platform Featuring High Drug Loading and a Controlled Bystander Effect

Abstract

After significant effort over the last 30 years, antibody-drug conjugates (ADCs) have recently gained momentum as a therapeutic modality, and nine ADCs have been approved by the FDA to date, with additional ADCs in late stages of development. Here we introduce Dolaflexin, a novel ADC technology that overcomes key limitations of the most common ADC platforms with two key features: a higher drug-antibody ratio and a novel auristatin with a controlled bystander effect. The novel, cell permeable payload auristatin F-hydroxypropylamide undergoes metabolic conversion to the highly potent but less cell permeable auristatin F to balance the bystander effect through drug trapping within target cells. We conducted studies in mice, rats, and cynomolgus monkeys to complement in vitro characterization and contrasted the performance of Dolaflexin with regard to anti-tumor activity, pharmacokinetic properties, and safety in comparison to the ADC platform utilized in the approved ADC ado-trastuzumab emtansine. A HER2-targeted Dolaflexin ADC was shown to have a much lower threshold of antigen expression for potent cell-killing in vitro, was effective in vivo in tumors with low HER2 expression, and induced tumor regressions in a xenograft model that is resistant to adotrastuzumab emtansine.

Targeting cancer with antibody-drug conjugates: Promises and challenges

“…The payload auristatin F-hydroxypropylamide (AF-HPA) is membrane-permeable and capable of bystander killing, but it is further metabolized to the membrane-impermeable auristatin F (AF), locking the payload molecules within the cell to achieve "controlled bystander effect" (termed DolaLock). 80 Preclinical data showed time-dependent accumulation of both AF-HPA and AF in cultured cancer cell lines and in xenograft tumors. 81,82 Several novel antibody platforms are being applied to ADC development strategies.…”

Targeted Drug Delivery and Theranostic Strategies in Malignant Lymphomas

“…For example, the fleximer linker used in upifitamab rilsodotin (XMT-1536), an ADC directed against sodium-dependent phosphate transport protein 2 (BNaPi2b) and loaded with auristatin, is a biodegradable, highly biocompatible, water-soluble polymer, to which are attached multiple molecules of the auristatin drug yielding a DAR between 12 and 15 [51]. The toxic warheads will broaden beyond antimicrotubule agents to other potent cytotoxic or targeted drugs including topoisomerase inhibitors (e.g., exatecan), alkylating agents (e.g., pyrrolobenzodiazepines), BH3 mimetics ( e.g., BCL2 inhibitors), or immunostimulants (e.g., toll-like receptor agonists) [52]. For example, huXBR1-402-G5-PNU, a novel anti-ROR1 ADC, is loaded with a highly potent anthracycline derivative of nemorubicin (PNU-159682) and demonstrated promising clinical activity in preclinical models of MCL after the failure of CAR19 T-cell-based therapy [53].…”

Antibody-Drug Conjugates: Functional Principles and Applications in Oncology and Beyond

“…In contrast to MMAE, MMAF does not exert bystander killing activity. A novel auristatin payload, auristatin F-hydroxypropylamide (AF-HPA), has been recently reported in the context of the pioneering ADC platform [80]. Interestingly, the membrane permeating AF-HPA undergoes intracellular conversion to membrane non-permeating MMAF, resulting in a controlled bystander effect.…”