Karyopharm kicks the Xpovio can to an uncertain 2024

The sellside appears remarkably unconcerned about Karyopharm’s plan to go back to the drawing board with a pivotal Xpovio endometrial cancer study that will not read out until mid-2024. Yesterday the group’s plan to use the dubious dataset generated by the Siendo trial fell apart when the FDA said Siendo was “unlikely” to support approval and called for a new study, sending Karyopharm down 40%. Xpovio is marketed for multiple myeloma, and Siendo represented its nearest-term opportunity to break into solid cancers, specifically as maintenance for patients responding to front-line chemo for endometrial cancer. But the sellside’s treatment of this as a mere delay ignores the fact that this market is changing fast; Glaxosmithkline’s Jemperli and Merck & Co/Eisai’s Keytruda plus Lenvima carry second-line labels, and the former faces the imminent readout of the Ruby trial, which includes a maintenance phase. Perhaps the most significant catalyst is the Due-E study of Astrazeneca’s Imfinzi plus chemo first line, followed by Imfinzi with or without Lynparza as maintenance, reading out next year. Xpovio might yet yield a positive result in 2024, but by then the endometrial cancer landscape might have changed markedly.