Abstract
Carfilzomib (CFZ) is a proteasome inhibitor used for oncology indication such as treating multiple myeloma. CFZ is a potent cytotoxic agent with an IC50 in nanomolar range in various cancer cell lines and was considered as a potential payload for antibody drug conjugates (ADCs). However, the conjugated CFZ to anti-CD22 or anti-HER2 antibody totally abolishes the in vitro potency. This was a surprise since with other payload such as monomethyl auristatin E (MMAE) where a potent anti-proliferation efficacy was retained as MMAE alone or as a payload in an ADC. Further investigations were conducted using CFZ alone, CFZ with a linker and CFZ-ADC with tissue matrices including lysosomal enzymes. With CFZ linked to the ADC, cathepsin B (lysosomal enzyme) was efficient in liberating CFZ from the ADC by cleavage of valine-citrulline linker. At the same time, the liberated CFZ in the lysosome was inactivated by further metabolism by lysosomal enzymes. The metabolic profiles demonstrated that the products from epoxide and amide hydrolysis were identified from these incubations. These results suggested that the CFZ-ADC upon uptake and internalization specifically delivers CFZ payload to the lysosomes, where the CFZ was inactivated. On the other hand, CFZ by itself is not as vulnerable and could reach its target. Therefore, the lysosomal stability is an important criterion in the selection of a payload for making next generation of potent ADC therapeutics.
SIGNIFICANCE STATEMENT N/A
- The American Society for Pharmacology and Experimental Therapeutics