Assessing biosimilarity of Trastuzumab monoclonal antibody therapeutics using RNA sequencing of treated SKBR3 cells

Patents of some therapeutic monoclonal antibodies (mAb) used for cancer treatment are ending soon, allowing for the entry of similar analogs (biosimilars) onto the market. To have a biosimilar approved by health agencies, the manufacturer must typically demonstrate functional and physicochemical similarity between the biosimilar and the approved reference product. Functional similarity is often validated with cell-based assays, but the information gained is limited. In contrast, RNA-seq methods enable a sensitive transcriptomic analysis, providing detailed information on pathways and cellular responses. Trastuzumab inhibits signaling of the cell-surface receptor HER2, which is overexpressed in approximately 30% of all breast cancer patients. Here, we compare the functional effect of the mAb Trastuzumab and a corresponding biosimilar. The SKBR3 breast cancer cell line was treated with the reference product, Trastuzumab (Herceptin®), or a proposed biosimilar (ApoTras), and the cellular transcriptomes were analyzed by RNA-seq. Functional similarity was assessed using two statistical contrasts. One contrast evaluated the mechanism of action by comparing treated samples (Her and ApoTras, n = 16) vs. untreated controls (n = 8). The other contrast directly compared ApoTras (n = 8) vs. Her (n = 8) to determine differences in expression between treatments. A gene set overrepresentation analysis of DEG for mAb treatments revealed mechanisms of action, which were consistent with known trastuzumab effects.