CAT-02-106, a site-specifically conjugated anti-CD22 antibody bearing an MDR1-resistant maytansine payload yields excellent efficacy and safety in preclinical models.

Hematologically derived tumors make up similar to 10% of all newly diagnosed cancer cases in the United States. Of these, the non-Hodgkin lymphoma (NHL) designation describes a diverse group of cancers that collectively rank among the top 10 most commonly diagnosed cancers worldwide. Although long-term survival trends are improving, there remains a significant unmet clinical need for treatments to help patients with relapsed or refractory disease, one cause of which is drug efflux through upregulation of xenobiotic pumps, such as MDR1. CD22 is a clinically validated target for the treatment of NHL, but no anti-CD22 agents have yet been approved for this indication. Recent approval of an anti-CD22 antibody-drug conjugate (ADC) for the treatment of relapsed/refractory ALL supports the rationale for targeting this protein. An opportunity exists for a next-generation anti-CD22 antibody-drug conjugate (ADC) to address unmet medical needs in the relapsed/refractory NHL population. We describe a sitespecifically conjugated antibody-drug conjugate, made using aldehyde tag technology, targeted against CD22 and bearing a noncleavable maytansine payload that is resistant to MDR1-mediated efflux. The construct was efficacious against CD22(+) NHL xenografts and could be repeatedly dosed in cynomolgus monkeys at 60 mg/kg with no observed significantly adverse effects. Exposure to total ADC at these doses (as assessed by AUC(0-inf)) indicated that the exposure needed to achieve efficacy was below tolerable limits. Together, the data suggest that this drug has the potential to be used effectively in patients with CD22(+) tumors that have developed MDR1-related resistance to prior therapies. (C) 2017 AACR.