Kadcyla is a biologic drug used to treat breast cancer. It is a complex molecule that requires several manufacturing steps to produce. According to the sources provided, the commercial manufacturing process of Kadcyla involves the following steps:

1. Expression of the antibody: The first step is to produce the antibody, trastuzumab, using recombinant DNA technology. This involves inserting the gene for the antibody into a host cell, such as Chinese hamster ovary (CHO) cells, and allowing the cells to produce the protein.

2. Conjugation with DM1: The next step is to conjugate trastuzumab with the cytotoxic agent, DM1. This is done using a chemical linker that attaches DM1 to the antibody. The resulting molecule is called trastuzumab emtansine or T-DM1.

3. Purification: The T-DM1 molecule is then purified using a series of chromatography steps to remove impurities and isolate the desired product.

4. Formulation: The purified T-DM1 is then formulated into the final drug product, Kadcyla. This involves adding excipients, such as buffers and stabilizers, to ensure the drug is stable and can be stored for an extended period.

5. Quality control: Throughout the manufacturing process, quality control tests are performed to ensure the drug product meets the required specifications for potency, purity, and safety.

In summary, the commercial manufacturing process of Kadcyla involves several steps, including the expression of the antibody, conjugation with DM1, purification, formulation, and quality control. These steps are necessary to produce a safe and effective drug product for the treatment of breast cancer.

Sources:
[1] Drug Patent Watch. Kadcyla. https://www.drugpatentwatch.com/p/biologics/tradename/KADCYLA
[2] Barok, M. et al. Trastuzumab emtansine: mechanisms of action and drug resistance. Breast Cancer Res. 2014; 16(2): 209. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5058630/
[3] European Medicines Agency. Kadcyla EPAR - Public assessment report. 2013. https://www.ema.europa.eu/en/documents/assessment-report/kadcyla-epar-public-assessment-report_en.pdf