Ver­sus Ver­tex, Pro­teosta­sis' triplet CF da­ta fall short, wilt­ing stock

It’s too lit­tle, too late for lit­tle Pro­teosta­sis Ther­a­peu­tics.

The Boston drug de­vel­op­er that is look­ing to take on Ver­tex Phar­ma­ceu­ti­cals — and the com­pa­ny’s en­trenched slate of cys­tic fi­bro­sis med­i­cines — re­port­ed da­ta from a mid-stage study test­ing its own CF triplet on Tues­day. The re­sults failed to im­press, sink­ing the stock $PTI more than 42% to $2.51 in pre­mar­ket trad­ing.

The tri­al test­ed Pro­teosta­sis’ diro­caftor (or PTI-808), and posen­caftor (or PTI-801) with or with­out neso­li­caftor (or PTI-428) against a place­bo in a four-week Phase II study in CF pa­tients. Over­all, 28 F508del ho­mozy­gous and 40 F508del het­erozy­gous sub­jects were en­rolled in the dou­blet, triplet or place­bo arms. CF is caused by a de­fec­tive and/or miss­ing CFTR pro­tein re­sult­ing from cer­tain mu­ta­tions in the CFTR gene — the F508del mu­ta­tion is one of the most com­mon.

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