In what is shaping up to be a back-loaded month, the FDA is set to release a slew of regulatory decisions in February, including two that would expand the labels of blockbuster drugs.
REGENXBIO Readies for Hunter Decision After Delay
Kicking off the month is REGENXBIO, which by Feb. 8 is expecting the FDA’s verdict on its Hunter syndrome gene therapy RGX-121. The Maryland-based biotech had originally expected a decision on RGX-121 by Nov. 9, but the FDA extended the deadline by three months to allow time to review longer-term clinical data submitted by REGENXBIO.
Also known as mucopolysaccharidosis II, Hunter syndrome is a rare condition caused by mutations in the iduronate-2-sulfatase (IDS) gene, resulting in a dysfunctional enzyme that under healthy circumstances helps degrade waste inside the cell. The toxic buildup of cellular waste, in turn, leads to hallmark symptoms of Hunter syndrome, such as developmental delay and growth abnormalities.
RGX-121 delivers a functioning copy of the IDS gene and restores the body’s ability to produce healthy levels of the corresponding enzyme. Data from the Phase I/II/III CAMPSIITE study, released in February 2024, showed an 86% median reduction in DS26, a disease biomarker indicative of brain disease activity.
DS26 levels approached normal in the study, REGENXBIO said at the time.
RGX-121 has the potential to become the first one-time therapy that targets the underlying cause of Hunter syndrome, according to an August 2025 news release from the company.
Merck Looks to Expand Keytruda Into Ovarian Cancer
Merck is seeking to add another indication to the more than 40 for which its blockbuster cancer drug Keytruda is already approved.
By Feb. 20, the FDA is expected to release its decision on the proposed combination of the PD-1 inhibitor with chemotherapy, with or without Roche’s Avastin, for the treatment of platinum-resistant recurrent ovarian cancer.
To support its application, Merck submitted data from the Phase III KEYNOTE-B96 trial, which in October last year demonstrated a 30% improvement in progression-free survival versus placebo, and a 24% drop in the risk of death from all causes. Nearly all patients experienced toxicities related to the study’s investigational regimen, leading to death in 0.9% of patients. In comparison, 1.6% of placebo counterparts died due to side effects.
Keytruda has not yet been approved to treat any kind of ovarian cancer.
Vanda Awaits Verdict for Bysanti in Bipolar I, Schizophrenia
Vanda Pharmaceuticals is proposing its atypical antipsychotic Bysanti for the treatment of acute bipolar I disorder and schizophrenia. The FDA’s decision is expected on Feb. 21.
Bysanti’s active ingredient is milsaperidone, an active metabolite of iloperidone, which is also owned by Vanda and is approved under the brand name Fanapt for the same indications that Bysanti is targeting.
In a March 2025 news release, Vanda said that when taken orally, Bysanti converts to Fanapt and that the two drugs have been shown in clinical studies to be “bioequivalent at both low and high doses.” The company backed this claim with pharmacokinetic data showing comparable changes in levels over time between the two drugs.
Given this chemical similarity, Vanda is supporting Bysanti’s application with studies described in Fanapt’s label. The safety package for Bysanti will also include data from Fanapt’s clinical development as well as post-marketing experience with the drug, covering more than 80,000 patient-years of exposure.
Taiho Proposes Combo Regimen of Inqovi for Leukemia
Taiho Oncology is combining its cancer drug Inqovi with AbbVie and Roche’s BCL-2 inhibitor Venclexta for the treatment of acute myeloid leukemia (AML). A verdict is expected on Feb. 25.
Specifically, Taiho is proposing the combination in patients who are unable to undergo intensive induction chemotherapy. In the Phase IIb ASCERTAIN-V study, the investigational regimen elicited a complete response rate of 46.5%. Lowering the bar to include complete responders with incomplete hematologic recovery bumped this rate up to 63.4%, according to a May 2025 publication in the Journal of Clinical Oncology.
Inqovi combines two drugs: the nucleoside metabolic inhibitor decitabine and the cytidine deaminase inhibitor cedazuridine. The first chemical triggers the death of cancer cells, while the second increases the overall systemic exposure of decitabine. Inqovi was first approved by the FDA in July 2020 for the treatment of myelodysplastic syndromes.
If approved for this indication, Inqovi would become the first all-oral alternative to current AML therapies, Taiho CMO Harold Keer said in a July 2025 news release.
Eton Targets Diabetes Insipidus With Oral Solution
By Feb. 25, the FDA is expected to release its decision on Eton Pharmaceuticals’ ET-600, an oral desmopressin solution, for the treatment of diabetes insipidus.
Affecting 1 in 25,000 people worldwide, diabetes insipidus is a rare disease characterized by the over-production of urine. The condition develops when the body fails to make enough vasopressin, an antidiuretic hormone that helps maintain fluid balance in the body. Desmopressin is a synthetic form of vasopressin.
Pivotal data in March 2025 showed that ET-600 is bioequivalent to an FDA-approved reference product containing the same active ingredients. Compared to commercial products, however, ET-600, if approved, “can accommodate the precise and titratable doses necessary for pediatric patients,” CEO Sean Brynjelsen said at the time.
Following Delay, Ascendis Awaits Decision on Dwarfism Drug
Late last year, the FDA pushed back by three months its decision date for Ascendis Pharma’s investigational achrondroplasia drug TransCon CNP. That extension is nearing its end, with a verdict expected by Feb. 28.
While it qualifies as a rare disease—achondroplasia affects around 15,000 to 40,000 newborns—it is nevertheless the most common cause of dwarfism. The disease is caused by a gain-of-function mutation in the FGFR3 gene, which ultimately suppresses the activity of cells involved in bone development. A crucial player in this pathway is C-type natriuretic peptide, a hormone that counteracts FGFR3.
TransCon CNP works by mimicking the function of this hormone and helps spur bone growth in patients. In the Phase II ACcomplisH trial, treatment improved annualized growth velocity to 5.42 cm per year, as compared with 4.35 cm per year in placebo comparators. A 2023 publication in The Lancet noted that this treatment benefit was statistically significant.
If approved, TransCon CNP is expected to pose a substantial challenge to BioMarin’s achondroplasia medicine Voxzogo. In its third-quarter earnings call in October last year, BioMarin walked back its previously set revenue goal of $4 billion by 2027, with CFO Brian Mueller pointing specifically to the “impact of potential Voxzogo” competitors.
BioMarin Targets Younger PKU Population for Palynziq
Looking to broaden its patient population, BioMarin is seeking a label expansion for its enzyme substitution therapy Palynziq, with a target action date of Feb. 28.
Specifically, the California company is looking to lower the age of eligibility for the drug to include adolescents from 12 through 17 years with phenylketonuria (PKU). Palynziq is currently only indicated for adults who have uncontrolled blood phenylalanine levels.
Data from the Phase III PEGASUS study, released in September last year, showed that Palynziq treatment lowered blood phenylalanine levels by 49.7% on average at 72 weeks, as compared with dietary adjustments alone. Mean baseline phenylalanine was 1,026.4 µmol/L and nearly half of patients had concentrations above 1,000 µmol/L.
Nearly half of treated patients saw at least a 50% reduction in phenylalanine levels at 72 weeks, BioMarin added at the time.
PKU is a genetic disease that renders the phenylalanine hydroxylase enzyme dysfunctional, in turn disrupting the normal metabolism of phenylalanine, commonly found in many protein-containing foods. Patients with this condition suffer from the complications of phenylalanine buildup, such as seizures, tremors and intellectual disabilities.
Sanofi, Regeneron Eye Another Indication for Dupixent
Capping off this list is Sanofi and Regeneron’s blockbuster drug Dupixent, which the partners are proposing for the treatment of allergic fungal rhinosinusitis (AFRS). The FDA’s verdict is expected on Feb. 28.
AFRS is a distinct subtype of chronic rhinosinusitis characterized by an excessive inflammatory reaction at the sinuses, driven by a hypersensitivity to fungi. Patients often suffer from nasal congestion and thick mucus discharge, and the condition can lead to nasal polyps, poor quality of life and even bone deformation around the sinus cavities. Current treatments include surgery and a lengthy course of systemic steroids.
Sanofi and Regeneron are supporting their expansion bid with data form the Phase III LIBERTY-AFRS-AIMS study, which in November last year demonstrated a 50% improvement in nasal congestion at 52 weeks, as compared with 9.8% in placebo comparators. Dupixent likewise hit key secondary endpoints, including patient-reported nasal obstruction, nasal polyp size and the need for corticosteroids or surgery.
