In vitro feasibility study of a protein replacement therapy for methylmalonic acidemia with homocystinuria CblC type: delivery of recombinant human MMACHC proteins into primary fibroblasts from CblC patients

CblC is a rare disorder caused by mutations in the MMACHC gene responsible for impaired conversion of vitamin B12, leading to accumulation of homocysteine (HCY) and methylmalonic acid (MMA). Clinical manifestations are highly variable. Despite the treatment with vitamin B12, betaine and folic acid, long-term response is unsatisfactory. The unfavorable outcome suggests that better understanding of the CblC pathophysiology is needed to improve treatment protocols and to develop new therapeutic approaches. We expect that our project will pave the way to a therapeutic strategy to cure patients affected by methylmalonic acidemia with homocystinuria, type C (CblC). Specifically, we intend to demonstrate in vitro that this multisystem disease can be treated with a protein replacement therapy (PRT) approach. Our objective is to restore the normal metabolic pathways of diseased cells by delivering human recombinant methylmalonic acidemia and homocystinuria type C protein (r-h-MMACHC) into human fibroblasts obtained from CblC patients. We plan to test two different delivery strategies to optimize protein transduction using cell penetrating peptides covalently or non-covalently bound to protein and assess the levels of HCY and MMA in culture media of supplemented cells. Demonstration that delivery of r-h-MMACHC restores affected cells metabolism will put us in the condition to next concentrate on the development of a PRT in compliance with regulatory requirements.