The FDA on Wednes­day not on­ly ap­proved the first gener­ic ver­sions of the decades-old di­a­betes in­sipidus treat­ment va­so­pressin, but al­so si­mul­ta­ne­ous­ly of­fered a par­tic­u­lar­ly damn­ing re­buke of a cit­i­zen pe­ti­tion at­tempt­ing to block the gener­ic, while promis­ing to pass along the mat­ter to the Fed­er­al Trade Com­mis­sion.

The re­sponse could prove trou­ble­some for the spon­sor of the brand name ver­sion of the drug, En­do’s Par Ster­ile Prod­ucts, which brought in more than $780 mil­lion in 2020 for its brand name ver­sion of the drug Va­sostrict.

Last month, Par’s lawyers at Ax­inn called on the FDA to re­frain from ap­prov­ing any gener­ics for Va­sostrict due to the po­ten­tial for cer­tain sta­bil­i­ty and oth­er spec­i­fi­ca­tions that could cause con­cerns with im­pu­ri­ties or oth­er safe­ty is­sues.

But FDA points out at the top of its re­sponse that va­so­pressin has been mar­ket­ed as a ther­a­peu­tic agent for near­ly a cen­tu­ry.

“Pitressin, a nat­ur­al va­so­pressin prod­uct de­vel­oped as an ex­tract of the bovine pos­te­ri­or pi­tu­itary, was first in­tro­duced in 1928,” the agency said.

What’s more is that Par on­ly won FDA ap­proval for va­so­pressin in the first place, in 2014, be­cause of the FDA’s drug safe­ty ini­tia­tive at the time to en­cour­age man­u­fac­tur­ers to ob­tain the agency’s ap­proval for old, un­ap­proved drugs.

In ad­di­tion to the deny­ing the pe­ti­tion, FDA said that it “does not on its face raise valid sci­en­tif­ic or reg­u­la­to­ry is­sues” and “it ap­pears to have been sub­mit­ted with the pri­ma­ry pur­pose of de­lay­ing ap­proval of Ea­gle’s AN­DA and fails to raise valid sci­en­tif­ic or reg­u­la­to­ry is­sues. The Agency in­tends to re­fer this mat­ter to the Fed­er­al Trade Com­mis­sion (FTC), which has the ad­min­is­tra­tive tools and the ex­per­tise to in­ves­ti­gate and ad­dress an­ti­com­pet­i­tive busi­ness prac­tices.”

This kind of ac­tion from the FDA is rare to see, as lawyer Kurt Karst at Hy­man, Phelps & Mc­Na­ma­ra not­ed on Twit­ter, and it may be part of a wider col­lab­o­ra­tion be­tween the FDA and FTC to put com­pa­nies on no­tice over at­tempts to block fu­ture gener­ics.

Gilead recently decided to pull two indications for its cancer drug Zydelig — in relapsed follicular B-cell non-Hodgkin lymphoma (FL) and relapsed small lymphocytic leukemia (SLL) — after failing to complete the confirmatory trials required as part of the accelerated approvals from 2014.

“As the treatment landscape for FL and SLL has evolved, enrollment into the confirmatory study has been an ongoing challenge,” Gilead said in a statement, noting it formally notified the FDA of its decision to voluntarily withdraw these indications.

While the US biosimilars industry has generally been a disappointment since its inception, with FDA approving 33 biosimilars since 2015, just a fraction of those have immediately followed their approvals with launches. And more than a handful of biosimilars for two of the biggest blockbusters of all time — AbbVie’s Humira and Amgen’s Enbrel — remain approved by FDA but still have not launched because of legal settlements.