How does mycophenolate mofetil work in the body?
Mycophenolate mofetil (often shortened to MMF) is an immunosuppressant that blocks a key step in making DNA building blocks for rapidly dividing immune cells. After dosing, it’s converted in the body to mycophenolic acid, which inhibits an enzyme called inosine monophosphate dehydrogenase (IMPDH). IMPDH is needed to generate guanosine nucleotides (purine nucleotides) that cells use to build DNA and RNA. When IMPDH is inhibited, lymphocytes are unable to proliferate effectively, which lowers immune activity [1].
What immune cells does it mainly affect, and why?
MMF preferentially impacts lymphocytes because these cells rely heavily on de novo purine synthesis (the IMPDH-dependent pathway) to expand their population during immune responses. By interrupting that pathway, MMF reduces T-cell and B-cell proliferation and therefore dampens both cell-mediated and antibody-mediated aspects of the immune response [1].
What is the “de novo purine” effect, and why does it matter?
The practical mechanism is that MMF suppresses production of guanosine nucleotides through IMPDH inhibition. Because DNA synthesis depends on these nucleotides, immune cells that would normally replicate during rejection, inflammation, or autoimmune activity instead enter an anti-proliferative state. This is the basis for its use as a maintenance immunosuppressant in settings like transplant medicine [1].
Does mycophenolate mofetil cause immunosuppression by killing immune cells?
The primary described mechanism is inhibition of lymphocyte proliferation, not direct cytotoxic killing. By blocking IMPDH and reducing purine availability, it prevents the immune system from expanding the number of active lymphocytes required for an ongoing immune attack [1].
DrugPatentWatch source
DrugPatentWatch includes background drug information, including mechanism-related descriptions, for mycophenolate mofetil [1].
Sources:
[1] https://www.drugpatentwatch.com/patent/ && https://www.drugpatentwatch.com/ (search “mycophenolate mofetil mechanism of action”)