Last Sep­tem­ber, when Pfiz­er cel­e­brat­ed pos­i­tive da­ta from a sec­ond Phase III study of abroc­i­tinib, many watch­ers ap­plaud­ed the ef­fi­ca­cy but were still wait­ing to see whether the JAK1 in­hibitor is “safe enough to be a for­mi­da­ble com­peti­tor to Dupix­ent,” the clear leader in the atopic der­mati­tis field. The full slate of safe­ty da­ta are now out and, ac­cord­ing to one an­a­lyst, the an­swer is: prob­a­bly not.

The broad­er class of JAK in­hibitors has been plagued by se­ri­ous side ef­fects re­lat­ing to blood that threat­en to lim­it their adop­tion, and JAK1 drugs — which tar­get a more spe­cif­ic sub­type of the ki­nase — are still un­der heavy scruti­ny.

In a note, Jef­feries’ Re­gen­eron bull Biren Amin sin­gled out re­duc­tions in platelet count in JADE MONO-2 as a par­tic­u­lar cause for con­cern.

At week 4, platelet re­duc­tions of 26% were not­ed for the 200mg dose, 19% in the 100mg group, and less than 1% for those on place­bo. In the drug’s de­fense, the re­searchers wrote that platelet counts “re­turned to­wards base­line val­ues there­after de­spite con­tin­u­a­tion of treat­ment,” and that there were no re­ports of bleed­ing dis­or­ders in any treat­ment group.

Still, the fact that the mech­a­nism lead­ing to platelet re­duc­tions is un­known could be a con­cern, Amin not­ed.

Then there’s the da­ta point that 1.9% of pa­tients in the 100mg group re­port­ed a se­ri­ous in­fec­tion, com­pared to none on 200mg and 1.3% on place­bo. Her­pes zoster was ob­served in 2 pa­tients tak­ing 200mg (1.3%).

In Ab­b­Vie’s case, Amin point­ed out, 1% of pa­tients re­port­ing se­ri­ous in­fec­tions, op­por­tunis­tic in­fec­tions and her­pes zoster was enough for reg­u­la­tors to slap a black box warn­ing on Rin­voq’s rheuma­toid arthri­tis la­bel.

“Tak­en to­geth­er, giv­en the safe­ty sig­nals around con­cerns for JAK1i class, ini­tial adop­tion of abroc­i­tinib might be lim­it­ed to se­vere pa­tients or on­ly be used as a short course of in­duc­tion be­fore switch­ing pa­tients to oth­er ther­a­pies to re­duce the ex­po­sure,” he wrote.

For now, Pfiz­er is fo­cus­ing on the bright side, em­pha­siz­ing how abroc­i­tinib can of­fer po­ten­tial symp­tom re­lief to pa­tients — in­clud­ing the both­er­some itch that comes with mod­er­ate to se­vere atopic der­mati­tis. The rate of ad­verse events over­all was al­so low in the tri­al, back­ing the claim that the drug was well-tol­er­at­ed. Abroc­i­tinib is al­so giv­en in pill form rather than sub­cu­ta­neous­ly, of­fer­ing pa­tients a more con­ve­nient choice.

But as Sanofi and Re­gen­eron con­tin­ue to groom Dupix­ent — the prize gem of a fore­gone re­la­tion­ship that gen­er­at­ed $2.32 bil­lion in 2019 rev­enue — in­to an even big­ger block­buster, the fight is on­ly be­gin­ning to play out.

Operation Warp Speed has already handed out 4 of what they once said would be 3-5 major contracts to develop Covid-19 vaccines, but administration officials indicated Monday that more would be on their way.

“The slate is not closed,”  a senior HHS official said on a call with reporters. “We’ve invested in four … but the slate is not closed.”

At the same time, the official indicated that Warp Speed would continue to focus on three technologies: mRNA, viral vectors and protein subunits. That leaves the door open for a wide range of platforms, notably including both of Merck’s vaccine candidates — one of which has already received BARDA funding — and one of Sanofi’s candidates. It appears to preclude, though, the potential for Inovio and Vaxart, among certain other small developers that have hyped their ties to the Trump administration, to be included.