Lenvatinib Mesylate is the mesylate form of Lenvatinib, which is obtained by the reaction of lenvatinib with one mole equivalent of mesylate. Both Lenvatinib and Lenvatinib Mesylate are targeted therapeutic drugs for multi-kinase inhibitors, with similar mechanisms of action and indications. Both can be used to treat certain types of endometrial cancer, kidney cancer, liver cancer and thyroid cancer.

However, lenvatinib mesylate has different crystalline forms, which vary in solubility and stability. Therefore, its absorption, bioavailability and therapeutic effect will all be affected. Currently, lenvatinib mesylate is available in crystalline types A, B, C, F and I. Recently, researchers have discovered a new type of crystalline form (M crystal form). This crystal form has good solubility and excellent stability, making it more effective in treating diseases.

The preparation method of the M crystal form of lenvatinib mesylate is as follows: Add lenvatinib powder to acetonitrile to obtain a suspension, then add mesylate to the suspension, stir at room temperature and centrifuge to obtain a solid, and dry overnight to obtain the M crystal form. The stirring time should be over 20 hours, and the preferred drying condition is room temperature.

Alternatively, the crystal form B of lenvatinib can be suspended in acetonitrile, slowly added with acetonitrile solution of methanesulfonic acid, aged, and the resulting suspension can be vacuum filtered under nitrogen protection to obtain a wet cake, which is then vacuum dried to obtain the crystal form M.