Since late September, Mirum Pharmaceuticals has put a fourth medicine on the U.S. market, reported that its hepatitis delta antibody met the primary endpoint of a pivotal Phase 3 trial, and reported that its commercial lead drug met the primary endpoint of a second Phase 3 in a new pediatric population. Over the past month the shares have fallen about 10%, and they are down roughly 29% over three months, closing at $80.39 on October 23 against a 52-week high of $130 . Three pieces of good news, no re-rating.
Mirum is a Foster City rare-disease company that sells oral drugs for cholestatic liver disease, the family of conditions in which bile fails to drain properly, poisoning the liver and causing an itch severe enough to drive children to self-harm. Its franchise drug, LIVMARLI (maralixibat), blocks the ileal bile acid transporter so that bile acids are excreted rather than recycled. Alongside it sit two older bile-acid medicines, CHOLBAM and CTEXLI, and as of September a fourth product, ATEBRIOZ, for a rare bone disorder. The market capitalization is $5.22 billion . My argument is that at this price investors are paying roughly fair value for the commercial business and getting the pipeline — an approved-but-unlaunched drug, a hepatitis delta antibody with one Phase 3 win behind it and a second study reading out within weeks, and a label expansion into a population with no approved therapy — for close to nothing, because of a single regulatory setback in August on an asset nobody should have been capitalizing in the first place.
The August pre-NDA meeting is the hinge, and it broke the wrong thing
The de-rating has a date. On August 5 Mirum reported second-quarter net product sales of $176.2 million and raised full-year guidance to $680–700 million. In the same release it disclosed that at a pre-submission meeting the FDA had recommended conducting a Phase 3 study of volixibat, its second bile-acid-transporter drug, for cholestatic itch in primary sclerosing cholangitis — this after the agency had granted the program Breakthrough Therapy and Orphan Drug designations and after the pivotal VISTAS study had met its primary endpoint . The shares went from a $105.63 close that day into the high $70s overnight, recovered into the high $90s within two weeks, and then ground steadily lower through...