AstraZeneca’s gefurulimab met its primary endpoint, but has not managed to best the efficacy demonstrated by its rival therapies in a late-stage generalised myasthenia gravis (gMG) trial.
In the Phase III PREVAIL study (NCT05556096), the drug offered a statistically significant 1.6-point improvement in myasthenia gravis activities of daily living (MG-ADL) scores from baseline compared with placebo.
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Gefurulimab’s positive impact on MG-ADL was observed after one week of treatment, though this effect was maintained over the 26-week study period.
However, gefurulimab failed to meet the efficacy benchmark set by UCB’s Rystiggo (rozanolixizumab), which reduced MG-ADL values by up to 2.6 points in the Phase III MycarinG study.
The drug’s impact on MG-ADL scores was also lower than Regeneron’s Phase III candidate, cemdisiran, as well as AstraZeneca’s own gMG drugs, Soliris (eculizumab) and Ultomiris (ravulizumab), which triggered 2.3, 1.7, and 2.09-point drops in their respective late-stage trials.
Meanwhile, the complement 5 (C5) inhibitor significantly reduced quantitative myasthenia gravis (QMG) total scores, demonstrating a 1.8-point reduction from baseline by week four. By week 36, this effect was deepened, with patients experiencing a mean 2.1-point drop in QMG scores.
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By GlobalDataQMG is a common clinical outcome measure used in gMG to quantify a patient’s disease severity. It takes 13 different measures of muscular, motor and respiratory function into account, offering a broad view of a patient’s overall quality of life (QoL).
Gefurulimab’s impacts on MG-ADL and QMG scores were seen in patients with anti-acetylcholine receptor (AChR) antibody-positive disease, which constitutes 85% of the gMG population.
The subcutaneous (SC) drug’s safety and tolerability profile was similar to Soliris and Ultomiris. AstraZeneca gained the rights all three drugs through its $39bn acquisition of Alexion Pharmaceuticals in 2021.
Of the treatment-emergent adverse events (TEAEs) recorded in the gefurulimab arm, the majority were mild-to-moderate, with the most common events being headache, reactions at the injection site and diarrhoea.
Gefurulimab’s future in gMG
If gefurulimab were to gain approval in gMG, it would become the third targeted therapy AstraZeneca has commercialised in this market – joining Soliris and Ultomiris in an indication GlobalData valued at $6.1bn in 2024.
GlobalData is the parent company of Clinical Trials Arena.
Gefurulimab’s approval in gMG could be welcome news for AstraZeneca, as analysts at GlobalData forecast that both drugs will start to lose grip of their market share in the coming years.
While Ultomiris’ sales are expected to grow until 2029, analysts predict that its fortunes will change in 2030, with profits effectively halving between 2029 and 2033 from $2.41bn to $1.2bn.
It’s a similar story for Soliris, which is expected to peak sales-wise in 2026 at $1.5bn, where it will then see a steady decline to $1bn by 2033.
This drop in sales is likely driven by stiff competition from SC therapies such as UCB’s Zilbrysq (zilucoplan) and Rystiggo, as well as Argenx’s Vyvgart Hytrulo (efgartigimod alfa and hyaluronidase-qvfc), which offer enhanced patient convenience over intravenous (IV) alternatives.
While Soliris and Ultomiris may lose out on gMG market share moving forward, gefurulimab could offer renewed hope in the indication for AstraZeneca, as its SC administration follows the treatment paradigm’s progression to self-administered therapies.
