Roche is partnering with Phoenix Molecular Designs to develop a companion diagnostic (CDx) in triple-negative breast cancer (TNBC), the latter company announced Wednesday. PhoenixMD said Roche's CDx identifies RSK2 activation in human tumours, with CEO Sandra Dunn noting that "top-line data generated from our CDx is encouraging, and we look forward to applying these learnings to identify TNBC patients that may benefit from PMD-026 in our upcoming Phase I/Ib study."

In September, PhoenixMD announced that it raised $2.7 million to advance PMD-026 through investigational new drug (IND)-enabling studies and to develop a companion diagnostic to determine which patients have high levels of activated RSK2.

According to PhoenixMD, PMD-026 "is the first orally available small molecule inhibitor that targets RSK2, a prime drug target in multiple cancers." The company noted that the diagnostic assay developed through the collaboration will relay information on how active the RSK2 pathway is in TNBC and other cancers. "Preliminary data indicates that 80 percent of [TNBC] cases express activated RSK2," PhoenixMD said, adding "more broadly, researchers have investigated more than 300 biopsies and found that RSK2 is activated in 65 percent of tumours from a study of 13 different tumour types." 

Under the collaboration, whose financial terms were not disclosed, Roche will establish a CAP/CLIA certified protocol over the coming months for clinical tumour analyses. In future clinical trials, PhoenixMD said it will refine the precision of the RSK2 CDx in identifying patients who may benefit from PMD-026. The biopharmaceutical company added that it expects to file an IND application for PMD-026 in the near term.

In 2017, PhoenixMD unveiled preclinical data demonstrating that PMD-026 led to "70-percent inhibition of RSK signaling, blocking TNBC tumour growth in mice."

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