The European Medicines Agency (EMA) has recently published concerns over the mutagenicity of chloromethyl isopropyl carbonate (CMIC) https://www.hma.eu/human-medicines/cmdh/advice-from-cmdh.html#c7175.
This molecule is used in the preparation of tenofovir disoproxil fumarate (TDF), a common active pharmaceutical ingredient (API) used in the treatment of HIV and Hepatitis B. CMIC is typically used during the last step of synthesis and residues of this chemical can carry over into the final API.
At this time, the WHO Prequalification Unit– Medicines Assessment team (PQT/MED) is treating this impurity as a likely mutagenic compound, which means that the levels of this impurity must be decreased to a lower limit.
PQT/MED is contacting all tenofovir disoproxil fumarate API and finished pharmaceutical product manufacturers involved in prequalification procedures that use TDF in their products, asking them to lower the limit for this impurity.
Patients taking tenofovir-containing products should continue to use them, as these medicines are essential for control of serious diseases such as HIV and Hepatitis B. The benefit from continuing to take these products until the levels of CMIC are reduced is much greater than if the medicine is stopped.
(Note: If the medicine is stopped, loss of disease control may occur, with potentially serious consequences.)