Tuesday, Argenx SE (NASDAQ:ARGX) released topline results from the ADVANCE-SC study evaluating Vyvgart Hytrulo (efgartigimod alfa and hyaluronidase-qvfc) in adults with primary immune thrombocytopenia (ITP), an autoimmune disorder defined by a significantly reduced number of platelets in blood circulation.

The primary endpoint of a sustained platelet count response was not met (p=0.5081); 13.7% (17/124) of treated patients demonstrated a sustained platelet count response compared to 16.2% (11/68) of placebo patients.

Secondary endpoints were not met, including additional endpoints on International Working Group (IWG) responder status and mean platelet count change from baseline.

Results from the first study in the ITP registrational program, ADVANCE-IV, were reported in May 2022. The study met its primary and key platelet-derived secondary endpoints, showing that 21.8% of patients achieved a sustained platelet response.

ADVANCE-IV formed the basis of the regulatory submission for approval of Vyvgart IV for ITP in Japan, where a decision is expected in the first quarter of 2024.

William Blair writes that the outright failure across endpoints is surprising.

As ADVANCE-SC performed worse than ADVANCE-IV, it raises the question of whether the pharmacokinetics of Vyvgart SC were suboptimal in ITP, but even achieving a 22% response rate would not have resulted in a positive trial given the level of placebo.

Assuming no additional negative details that may suggest an underlying issue with Vyvgart Hytrulo, William Blair sees this as a buying opportunity ahead of several critical Phase 3 read-outs and continued commercial execution and reiterates the Outperform rating.

Price Action: ARGX shares are down 10% at $446.17 on the last check Tuesday.