Roche’s Genentech has put numbers behind its phase 3 IgA nephropathy win, reporting that sefaxersen reduced proteinuria by 43.1% compared with placebo at 37 weeks in the late-stage IMAgINATION trial. Proteinuria, the presence of excess protein in urine, is a key marker of kidney damage, making the result the central efficacy proof point Roche needed after saying last month that the study had met its primary endpoint.

The company also said that among patients who had blood in their urine at baseline, a greater proportion of those receiving sefaxersen saw that condition resolve versus placebo. Roche reported that the antisense oligonucleotide was well tolerated, with no new safety signals and a safety profile consistent with an earlier phase 2 trial.

The data

Roche presented the detailed results at the American Society of Nephrology's Kidney Week meeting in Denver. Sefaxersen is designed as a once-monthly subcutaneous injection and works by inhibiting production of complement factor B in the liver. That target sits in the immune system’s alternative complement pathway, whose overactivation contributes to kidney damage in IgA nephropathy.

The company plans to continue IMAgINATION to measure kidney function over two years while sharing the dataset with regulatory agencies “with the goal of bringing this treatment to patients as soon as possible.” That means the current result is important, but not the final clinical or regulatory word: Roche still needs the longer follow-up to build the broader case on disease progression.

The commercial picture

Roche licensed sefaxersen, previously called IONIS-FB-LRx, from Ionis Pharmaceuticals in 2022 after first signing an option agreement in 2018. The company has projected peak sales of 1 billion to 2 billion Swiss francs for the drug, showing that Roche sees IgA nephropathy as more than a niche renal opportunity.

That opportunity is already contested. Novartis won accelerated FDA approval for its own factor B inhibitor, Fabhalta, in 2024 and followed with full approval in July 2026. Fabhalta’s twice-daily oral dosing could be commercially attractive relative to Roche’s monthly injection, but Roche has pointed to a different trade-off: Fabhalta has been associated with increased cholesterol levels, while sefaxersen showed no such effect in a previous phase 2 study.

For Roche, the readout supports a strategy built around differentiation within an established mechanism. Rather than opening a new class, sefaxersen now has to prove that monthly administration and its safety profile can carve out space in a market where a direct competitor is already on the market.