Sparsentan

The path to blockbuster sales for Travere's Filspari will start with a gradual ramp into 2028, Evercore ISI analysts predict. With the path to blockbusterland now in sight, Travere Therapeutics is ready to hit the ground running after Monday’s landmark approval for Filspari in focal segmental glomerulosclerosis (FSGS). Filspari is the first approved product for rare kidney disease and is poised to reach an addressable FSGS patient population of over 30,000, the company said in a presentation following the approval. Given its experience with Filspari's 2023 green light for IgA nephrography (IgAN), Travere boasts an “execution-ready” commercial platform that can support “long-term, sustainable revenue growth,” it said. Together with the IgAN population that the drug already covers, Filspari now has the potential to reach over 100,000 patients, according to Travere. From a market watcher's perspective, Evercore ISI analysts have forecasted peak sales of $1.4 billion from Filspari’s newly granted FSGS indication, while sales tied to IgAN usage are on track to top out at $800 million, the analysts wrote in a recent note to clients. Travere, for its part, is eyeing an even higher target, estimating a potential peak sales opportunity of more than $3 billion for Filspari in the U.S.To get there, the company has outlined a detailed launch plan that includes a customized patient support program built around FSGS, a focus on patient and physician education, an over 100-person-wide field team and a payer access foundation that builds on Filspari’s IgAN positioning. With the green light, Travere is immediately making Filspari available in its new indication, which the company described as a perk of its “streamlined logistics.” Filspari’s new label stipulates its use to reduce proteinuria, or protein in the urine, in FSGS patients ages eight years old and older without nephrotic syndrome. The Evercore team noted that Filspari won a broad label encompassing multiple disease subtypes, aside from the “surprise” exclusion of patients with nephrotic syndrome, which is a kidney disorder hallmarked by a specific range of high proteinuria levels. Still, the analysts noted that the lack of a nephrotic-specific label only impacts some 15% of the real-world FSGS patient population. The label, as defined, can be attributed to Filspari, showing a greater reduction in proteinuria across the cohort of patients who didn’t have nephrotic syndrome in Travere’s Duplex trial, with a 39% reduction from baseline levels for those patients compared to the 22% seen in the overall study population, the company explained. Travere is moving quickly on its launch, given the “high urgency” to treat FSGS. With more than 75% of FSGS patients expected to progress to dialysis and around 75% of surveyed nephrologists calling the condition “extremely challenging” to manage, the company aims to capitalize on “awareness and desire” for the new product. Additionally, a significant crossover opportunity lies in the 80% prescriber overlap with healthcare providers who offer Filspari under its IgA nephrography indication, Travere noted.  In that flagship indication, Filspari has stood firm against IgAN competition from Novartis and currently holds the title of the “most commonly prescribed” FDA-approved med for IgAN to date, the company said. In 2025, full-year sales of Filspari grew 144% from 2024 to $322 million. In the near term, the Evercore analysts predict sales from Filspari’s new indication to ramp up from an anticipated $55 million in 2026 to $315 million in 2027, followed by an estimated $640 million in 2028.Travere navigated numerous hurdles on the trek toward Filspari's FSGS approval, which was delayed by three months after the FDA requested more information characterizing the drug’s clinical benefit. The phase 3 Duplex study missed its primary endpoint in 2023, prompting the creation of a new endpoint for FSGS clinical trials. Then, more recently, concerns about the FDA’s handling of rare disease drug approvals began to emerge, prompting concern about how Filspari would fare at the agency’s desk. Now, with the Filspari nod secured, the approval presents a “significant positive” for rare nephrology regulatory flexibility across the board, the Evercore analysts argued.