By MATTHEW PER­RONE, As­so­ci­at­ed Press

WASH­ING­TON (AP) — Gov­ern­ment health ad­vis­ers on Tues­day weighed the ben­e­fits and risks of a close­ly watched drug from Mer­ck that could soon be­come the first U.S.-au­tho­rized pill for pa­tients to take at home to treat COVID-19.

The Food and Drug Ad­min­is­tra­tion asked its out­side ex­perts whether the agency should au­tho­rize the pill, weigh­ing new in­for­ma­tion that it is less ef­fec­tive than first re­port­ed and may cause birth de­fects. A vote was ex­pect­ed Tues­day af­ter­noon. The pan­el’s rec­om­men­da­tions aren’t bind­ing but of­ten guide FDA de­ci­sions.

The meet­ing comes as U.S. in­fec­tions are ris­ing again and health au­thor­i­ties world­wide size up the threat posed by the new omi­cron vari­ant.

If au­tho­rized, Mer­ck’s pill would be the first that doc­tors could pre­scribe for pa­tients to take on their own to ease symp­toms and speed re­cov­ery, a ma­jor step to­ward re­duc­ing hos­pi­tal case­loads and deaths. The drug, mol­nupi­ravir, is al­ready au­tho­rized for emer­gency use in the U.K.

Giv­en the on­go­ing threat, the FDA is wide­ly ex­pect­ed to ap­prove emer­gency use of Mer­ck’s pill. But new da­ta re­leased last week paint­ed a less com­pelling pic­ture than when the the com­pa­ny first pub­li­cized its ear­ly re­sults in Oc­to­ber.

Last week, Mer­ck said fi­nal study re­sults showed mol­nupi­ravir re­duced hos­pi­tal­iza­tion and death by 30% among adults in­fect­ed with the coro­n­avirus, when com­pared with adults tak­ing a place­bo. That ef­fect was sig­nif­i­cant­ly less than the 50% re­duc­tion it first an­nounced based on in­com­plete re­sults.

FDA sci­en­tists said Tues­day the rea­sons for the dif­fer­ence were un­clear, but ap­peared to be due to high­er-than-ex­pect­ed hos­pi­tal­iza­tions among pa­tients tak­ing the drug dur­ing the sec­ond half of the study. Mol­nupi­ravir’s ef­fec­tive­ness is a key con­sid­er­a­tion as pan­el mem­bers weigh whether to rec­om­mend the drug and for whom.

An­oth­er ques­tion is whether preg­nant women or women of child-bear­ing age should avoid the drug.

FDA sci­en­tists said Tues­day that com­pa­ny stud­ies in rats showed the drug caused tox­i­c­i­ty and birth de­fects in the skele­ton, eyes and kid­neys. Tak­en to­geth­er, FDA staffers con­clud­ed the da­ta “sug­gest that mol­nupi­ravir may cause fe­tal harm when ad­min­is­tered to preg­nant in­di­vid­u­als.”

Reg­u­la­tors said they are con­sid­er­ing bar­ring mol­nupi­ravir’s use dur­ing preg­nan­cy or warn­ing against it but leav­ing it as an op­tion in rare cas­es. The FDA al­so pro­posed that doc­tors ver­i­fy pa­tients are not preg­nant be­fore start­ing treat­ment and rec­om­mend con­tra­cep­tives while pa­tients take the pills.

In its own pre­sen­ta­tions Tues­day, Mer­ck said it is not rec­om­mend­ing the drug be used in women who are preg­nant or lac­tat­ing. But the drug­mak­er op­posed a blan­ket re­stric­tion on pre­scrib­ing to those pa­tients, ar­gu­ing there may be cer­tain cas­es where the drug’s ben­e­fit out­weighs its risk.

The drug us­es a nov­el ap­proach to fight COVID-19: It in­serts tiny er­rors in­to the coro­n­avirus’ ge­net­ic code to stop it from re­pro­duc­ing. That ge­net­ic ef­fect has raised con­cerns that the drug could spur more vir­u­lent strains of the virus. But FDA reg­u­la­tors said Tues­day that risk is the­o­ret­i­cal and seems un­like­ly.

Mer­ck sci­en­tists said they be­lieve their drug will be ef­fec­tive against the new omi­cron vari­ant. They said the drug worked against oth­er vari­ants, in­clud­ing the pre­vail­ing delta strain.

Pan­elists are al­so weigh­ing whether the pills should be of­fered to pa­tients who have been vac­ci­nat­ed or pre­vi­ous­ly had COVID-19. Mer­ck didn’t study the drug in vac­ci­nat­ed peo­ple, but da­ta from a hand­ful of pa­tients with pri­or in­fec­tions sug­gest­ed it had lit­tle ben­e­fit. Still, it may be im­prac­ti­cal for doc­tors to screen out those pa­tients. The Mer­ck drug works best when giv­en with­in five days of first COVID-19 symp­toms, un­der­scor­ing the need for speedy treat­ment.

Mer­ck test­ed the drug in adults with mild-to-mod­er­ate COVID-19 who were con­sid­ered high­er risk due to health prob­lems like obe­si­ty, di­a­betes or heart dis­ease. That’s the same group that cur­rent­ly re­ceives an­ti­body drugs, which help the im­mune sys­tem fight the virus. The FDA has au­tho­rized three an­ti­body drugs for COVID-19 but all have to giv­en by IV or in­jec­tion at hos­pi­tals or clin­ics.

Mer­ck was the first com­pa­ny to sub­mit its COVID-19 pill to the FDA, but a ri­val drug from Pfiz­er is close be­hind and is al­so un­der re­view.

Pfiz­er’s drug is part of a decades-old fam­i­ly of an­tivi­ral pills known as pro­tease in­hibitors, a stan­dard treat­ment for HIV and he­pati­tis C. They work dif­fer­ent­ly than Mer­ck’s pill and haven’t been linked to the kind of mu­ta­tion con­cerns raised with Mer­ck’s drug.

Pfiz­er said this week that its drug shouldn’t be af­fect­ed by the omi­cron vari­ant’s mu­ta­tions.