Dianthus Therapeutics is advancing its challenge for the increasingly competitive generalized myasthenia gravis (gMG) market, outlining plans to move into phase 3 on the back of hits in a midphase study.
The phase 2 trial compared two doses of claseprubart, an antibody engineered to selectively target the classical pathway, to placebo in 65 adults with AChR-positive gMG. Patients received claseprubart every two weeks via subcutaneous injection. While the primary endpoint looked at safety and tolerability, the secondary endpoint data provided a glimpse of the efficacy of the drug candidate.
At the low dose, Dianthus reported a 4.6-point improvement on MG-ADL, a scale that measures the impact of gMG on daily functions. The improvement rose to 5.4 points on the high dose. Adjusted for placebo, the improvements on the low and high doses were 1.8 points and 2.6 points, respectively.
Dianthus shared the results alongside data on QMG, a physician's score of disease severity. QMG scores improved 4.4 points and 4.5 points, respectively, on the low and high doses. Scores improved by two points in the placebo arm. Dianthus also reported statistically significant improvements on other measures of gMG.
The biotech shared cross-trial comparisons to show how claseprubart performed against AstraZeneca’s Soliris and Ultomiris and UCB’s Zilbrysq. Claseprubart outperformed the competition in the data shared by Dianthus, with the caveat that such cross-trial comparisons can be unreliable.
The company found the drug candidate was generally well tolerated, giving it a data set to inform talks with the FDA and preparations for phase 3. Dianthus plans to test two regimens of the low dose in phase 3, with patients receiving the study drug every two or four weeks.
Dianthus didn’t test four-week dosing in the phase 2 study, but the lack of statistical difference between the low and high doses, coupled with evidence such as half-life data, led it to speculate that a less-frequent regimen could work. The two-week dose is Dianthus’ target product profile, but CEO Marino Garcia sees an opportunity to go beyond the base case.
“Why not go further? Why not push that differentiation? I don't see much of a downside to be honest,” Garcia said on a call with investors to discuss the data.
Dosing is central to Dianthus’ plans to differentiate its candidate in a competitive market. The company said more than 80% of patients with AChR-positive gMG have yet to switch to a biologic, despite the availability of C5 inhibitors such as Ultomiris and FcRn drugs, including argenx’s Vyvgart. Dianthus has identified intravenous and high-volume subcutaneous dosing as a barrier to uptake of rival drugs.
That thinking led Dianthus to develop an autoinjector. The overarching goal is to combine the efficacy of C5 inhibitors such as Ultomiris with the safety of C1 blockers such as Enjaymo and the convenience of Dupixent.
Analysts at Evercore ISI said in a note to clients that: “Both doses clearly met all the bull case efficacy bars” the firm had discussed in preview ahead these data. They added that the biotech “convincingly” matched the C5s. It didn’t see a dose response, thus “opening the door to a longer Q4W dosing interval.”