Mertansine (DM1) API Suppliers & Bulk Manufacturers

Available Forms: API (drug substance)

Available Strengths: Supplied to an in-house or pharmacopoeial specification

Reference Brands: Kadcyla

Category: Active Pharmaceutical Ingredient

Mertansine (DM1) is a maytansinoid tubulin inhibitor used as the cytotoxic payload in antibody-drug conjugates. It is sourced by ADC developers, bioconjugation CDMOs and R&D teams.

Product Description:

Mertansine, also called DM1, is a thiol-bearing derivative of maytansine that binds tubulin and stops cells dividing; it is far too toxic to be given alone and is used as the payload of antibody-drug conjugates. In trastuzumab emtansine, DM1 is attached to the antibody through the non-cleavable MCC linker, and that medicine is approved for HER2-positive metastatic breast cancer previously treated with trastuzumab and a taxane, and for HER2-positive early breast cancer with residual invasive disease after neoadjuvant treatment (reference brand: Kadcyla).

Specification at a glance

Regulatory files and timing

The FDA list of Drug Master Files (third quarter 2026) shows 5 active Type II API DMFs for this molecule. Few filings usually means few qualified sources, so early contact with suppliers pays off. For Europe, ask whether the supplier holds a CEP or an EU ASMF and, for imports into the EU, a written confirmation.

Generic or biosimilar entry. United States: No confirmed date (not documented). European Union: No confirmed date (not documented).

Handling and quality points

DM1 is among the most potent cytotoxics handled in pharmaceutical manufacture, so it needs isolator-level containment, dedicated equipment and occupational exposure limits well below one microgram per cubic metre. The free thiol oxidises readily to the disulfide dimer, so ask how the supplier prevents and limits this, and agree inert-atmosphere packaging and cold storage based on stability data. As the material goes into a conjugation step, buyers also look at maytansinoid-related impurities that could react and carry through into the final ADC.

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Brand names are trademarks of their respective owners and identify the reference medicine only. Information is general and was checked in October 2026; confirm specifications and filings with the supplier before purchase.