OrphanPulse Wk 39: A 900-Patient Disease Now Has Two Approved Drugs

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OrphanPulse Wk 39: A 900-Patient Disease Now Has Two Approved Drugs

Athithi Verma·28 September 2026·12 min read·Synopulse
OrphanPulseDeep pine banner. A gold signal line climbs from lower left to a glowing teal node at upper right, scattered with small teal data points, beside the OrphanPulse wordmark under the Synopulse and The Pulse kicker. Synopulse · The Pulse OrphanPulse This week in rare disease Week of 21 to 27 September 2026

FDA approved Mirum and Incyte’s Atebrioz for fibrodysplasia ossificans progressiva on 25 September, the second approved therapy for a disease affecting about 900 people worldwide. It rests on one placebo-controlled Phase 2 cohort, licensed by Mirum five months before its PDUFA date. Elsewhere: ulefnersen became the first FUS-ALS trial to meet its primary endpoint, Europe approved the first drug for cerebral adrenoleukodystrophy, and Lantheus launched the first generic radioligand.

11
Developments
900
FOP patients
worldwide
31.0%
High-dose XLRP
responders
Jan 28
Arikayce
PDUFA
5
Also in
NeuroPulse
The lead · Approval

Mirum’s Atebrioz becomes the second approved FOP drug, carried by a pivotal Phase 2

FDA approved Atebrioz (zilurgisertib), an oral ALK2 inhibitor, for adult and paediatric patients with fibrodysplasia ossificans progressiva, Mirum Pharmaceuticals (Nasdaq: MIRM) and Incyte announced on 25 September, ahead of a 26 September PDUFA date under Priority Review. FOP is an ultra-rare genetic disease in which abnormal ALK2 signalling drives bone formation in muscle and connective tissue, known as heterotopic ossification, affecting approximately 300 patients in the US and 900 worldwide. Approval rests on Cohort 1 of the placebo-controlled pivotal Phase 2 PROGRESS study in patients aged 12 and over, which the companies reported at ENDO 2026 as showing reductions in total heterotopic ossification lesion volume, new lesions and flare activity. Mirum licensed worldwide rights from Incyte in April 2026. Ipsen’s Sohonos (palovarotene) was approved by FDA in 2023.

Regulatory note

Mirum licensed an asset five months before its PDUFA date and the approval arrived a day early. Buying a Priority Review NDA in April and launching in September is the cleanest possible rare disease in-licensing trade: Incyte had already retired the development risk, and Mirum bought a commercial asset for a population it can reach through the specialist centres its existing rare disease products already serve.

  • A second mechanism changes the treatment question. Sohonos works downstream through the retinoic acid receptor gamma and carries a risk of premature growth plate closure in children. Atebrioz blocks ALK2, the receptor whose mutation causes the disease. Expect clinicians to ask about sequencing and combination before either company has data on it.
  • Imaged lesion volume is now the regulatory currency. Both approvals rest on heterotopic ossification measured on imaging rather than a functional endpoint, which sets the evidentiary bar for every ALK2 programme behind them.
  • 900 patients worldwide is a pricing statement. With two approved drugs splitting a few hundred US patients, per-patient price rather than volume carries revenue, and payers now have an in-class comparator to negotiate against.
  • Check the label for post-marketing commitments. A single placebo-controlled Phase 2 cohort is a thin evidence base for a lifelong therapy started in adolescence, and the long-term extension is where the durability question gets answered.
The Intel / Ten to know
Ordered by strategic weight · Notes are typed by lens and are analysis, not company claims
01Approval · Cerebral adrenoleukodystrophyAlso in NeuroPulse

Europe approves leriglitazone as the first drug for cerebral adrenoleukodystrophy, under exceptional circumstances

The European Commission granted marketing authorisation on 25 September to Nezglyal (leriglitazone), Minoryx Therapeutics’ oral suspension, for cerebral adrenoleukodystrophy, following a positive CHMP opinion on 23 July. The authorisation is under exceptional circumstances; the CHMP recommendation covered boys aged 2 to 12 with gadolinium-negative brain lesions. It rested on the Phase 2/3 NEXUS1 study and real-world evidence from compassionate use. cALD is a demyelinating disease that can progress to neurological decline and death within three to four years. There was no approved pharmacological treatment in the EU, and Neuraxpharm is the commercial partner.

Access note

Exceptional circumstances is granted when complete data cannot be obtained, and it carries annual reassessment and specific post-authorisation obligations. Every member-state HTA body will read that as a conditional evidence position, so first approved in Europe and reimbursed in Europe are separate milestones here, and the second will arrive country by country.

  • The label is an early-disease window defined by MRI. Gadolinium-negative lesions precede active inflammation. Eligible boys come from MRI surveillance of those already known to carry ALD, which makes newborn screening coverage the real market size.
  • Transplant and gene therapy are the comparators. An oral drug competes on risk and logistics with haematopoietic stem cell transplant, not on replacing it, and is most likely to bridge or to serve boys ineligible for either.
  • CALYX 2 in adults is the next value step. Minoryx is generating data in adult men with enhancing lesions to support a US filing and an EU label expansion into a larger, sicker population.
02Clinical · FUS-ALSAlso in NeuroPulse

Ulefnersen becomes the first FUS-ALS trial to meet its primary endpoint

Ionis and Otsuka announced on 22 September that the Phase 3 FUSION trial of ulefnersen, an intrathecal antisense oligonucleotide targeting FUS mRNA, met its primary endpoint, a joint rank analysis of time to death or permanent ventilation, time to rescue and change in ALSFRS-R to Day 505 against placebo (p=0.0005). Neurofilament light chain and a composite of death, ventilation, rescue or withdrawal for progression also favoured ulefnersen. Most adverse events were mild or moderate. Otsuka opened an early access programme on 21 September. FUS mutations account for an estimated 43% to 52% of juvenile and paediatric ALS.

CI note

This is the first positive placebo-controlled trial in a genetic ALS subtype on a clinical composite. Tofersen reached approval on a neurofilament surrogate after missing its functional primary; ulefnersen has the clinical win, from the same Ionis antisense chemistry, which strengthens the case for every allele-targeted ALS programme behind it.

  • Early access came first and that is deliberate. A programme opened the day before topline means Otsuka had supply and eligibility ready, so patients reach drug before any filing is reviewed.
  • Paediatric onset raises the urgency and the burden. Juvenile FUS-ALS can progress to respiratory failure within one to two years, and repeated intrathecal dosing in children needs specialist centres.
  • Effect size is still undisclosed. Ask for the win ratio and the neurofilament change at congress, because they will decide the regulatory route.
03Clinical · X-linked retinitis pigmentosaAlso in NeuroPulse

Beacon’s laru-zova is the first XLRP gene therapy to win a pivotal trial

Beacon Therapeutics reported on 21 September that the Phase 2/3 VISTA trial of laruparetigene zovaparvovec (laru-zova), a subretinal AAV gene therapy delivering full-length RPGR, met its FDA-endorsed primary endpoint. VISTA randomised 85 males to high dose, low dose or untreated control. At 12 months, 31.0% of high-dose and 24.1% of low-dose patients gained at least 15 letters of low luminance visual acuity against none of the controls. Beacon plans a rolling BLA later in 2026, with full data at AAO on 10 October. Laru-zova holds RMAT, Fast Track, PRIME and Orphan Drug designations in a disease affecting an estimated 20,000 patients in the US and Europe.

CI note

A competing RPGR gene therapy missed its pivotal primary before this readout, so Beacon’s result resets the category rather than joining it. The untreated control, rather than a sham procedure, is the design point regulators will probe, and a zero control responder rate is the best answer Beacon could have.

  • The low dose won on 10-letter gains. 58.6% against 48.3% for the high dose is non-monotonic, and dose selection for the label is not settled.
  • Syncona now has a monetisable asset. It held its 38.4% stake at £183.4 million at 30 June and names financing, an IPO or a sale as next steps.
  • Launch will run through retinal surgeons. Subretinal delivery needs a vitrectomy, so uptake follows specialist centre capacity rather than prescriber demand.
04Access · Neuroendocrine tumours

Lantheus launches the first generic radioligand, and Lutathera loses its monopoly

FDA granted final approval on 22 September to Lantheus’ Bravnetsa (lutetium Lu 177 dotatate, formerly PNT2003) for adults with SSTR-positive gastroenteropancreatic neuroendocrine tumours, through the Abbreviated New Drug Application pathway. It is the first radioligand therapy approved by that route and the only radiopharmaceutical FDA has determined to be bioequivalent and therapeutically equivalent to Lutathera. Tentative approval came in March 2026, with final approval held behind a 30-month Hatch-Waxman stay that expired in June. A separate lutetium Lu 177 dotatate injection, Bexlutry, was also recently approved. Lantheus estimates about 200,000 people in the US live with GEP-NETs.

Access note

Therapeutic equivalence is the access finding, because it allows substitution. For the first time a radioligand enters the formulary mechanics that govern generic small molecules, although substitution will run through nuclear medicine purchasing contracts rather than at a pharmacy counter.

  • Supply decides the first year, not price. Lutetium-177 doses are made to order with short half-lives, and Lantheus names reliable supply as its launch focus. A generic that misses a treatment date is not a substitute.
  • Read it against the week’s biggest deal. Telix paid $1.65 billion for ITM, whose Phase III ITM-11 is a lutetium-based SSTR therapy in GEP-NETs, with up to $450 million of milestones tied to ITM-11 sales. It will launch into a market where the reference product now has two challengers.
  • Lantheus is itself being acquired. Curium agreed to buy Lantheus in the $8.0 billion deal covered in NeuroPulse Week 33, so Bravnetsa joins a combined isotope supplier.
05Clinical · Achondroplasia

Abbisko’s oral FGFR2/3 inhibitor adds 2.4 cm a year in seven children at its lowest dose

Abbisko Therapeutics reported preliminary Phase 2 results on 21 September for lavengratinib (ABSK061), an oral selective FGFR2/3 inhibitor, in achondroplasia. In the open-label, dose-escalation ABSK061-202 study, all seven children aged 6 to 12 in the lowest-dose cohort (0.064 mg/kg once daily) completed 27 weeks with a mean increase in annualised height velocity of 2.4 cm/year from baseline, and all met the 25% responder threshold. No serious adverse events, discontinuations, hyperphosphatemia or corneal toxicity were reported. Higher-dose cohorts continue, with a six-month dataset expected before the end of 2026. Lavengratinib holds Rare Pediatric Disease and Orphan Drug designations.

CI note

Seven children, open label and no control, in a field where the benchmarks are placebo-controlled. BridgeBio’s oral infigratinib added 1.74 cm/year over placebo in Phase 3 PROPEL 3, and vosoritide’s pivotal study added about 1.57 cm/year. A within-patient change of 2.4 cm/year is not comparable to either, because growth velocity in achondroplasia falls with age and uncontrolled baselines flatter the result.

  • Selectivity is the real differentiation. Hyperphosphatemia and corneal effects come from inhibiting other FGFR family members. Avoiding them at efficacious doses would be a safety argument against less selective oral competitors.
  • Formulation is a competitive feature here. Abbisko built mini-tablets under 3 mm for young children, and in a daily chronic paediatric therapy formulation drives adherence.
  • The realistic position is fast follower. Infigratinib has Phase 3 data; lavengratinib has 27 weeks in seven patients. The higher-dose cohorts decide whether it can be a better follower.
06Access · MAC lung disease

Insmed files to take Arikayce from refractory MAC lung disease to newly diagnosed patients

FDA accepted Insmed’s sNDA for Arikayce (amikacin liposome inhalation suspension) with Priority Review on 21 September, setting a PDUFA date of 28 January 2027. The application seeks full approval for MAC lung disease as part of a combination regimen, converting a 2018 accelerated approval restricted to refractory patients who had failed at least six months of multidrug therapy. It rests on the Phase 3b ENCORE study in 425 treatment-naive patients, which met its primary endpoint on Respiratory Symptom Score change at month 13 and multiplicity-controlled culture conversion secondaries. Insmed has not published conversion rates.

Access note

Moving from refractory to newly diagnosed patients multiplies the eligible population, because refractory patients are the minority who fail standard therapy. The access question is whether payers accept a symptom score as the primary for a drug whose value has always been argued on culture conversion.

  • The confirmatory obligation is arriving late. Accelerated approval in 2018 and a full approval decision in 2027 is nearly nine years on a surrogate, the timeline current FDA policy on accelerated approval is designed to shorten.
  • The missing numbers are the ones that set formulary position. No conversion rates, times to conversion or arm-level adverse event rates have been published yet.
  • Japan is next. Insmed will discuss ENCORE with the PMDA in Q4 2026, and a Japan-specific endpoint was built into the trial.
07Access · APDS

Pharming’s lower-dose Joenja filing for small children gets Priority Review before the first paediatric decision

FDA accepted Pharming’s sNDA for lower doses of Joenja (leniolisib) for children with APDS weighing under 27 kg and granted Priority Review, announced 25 September. It follows the separate resubmission for children aged 4 to 11 weighing 27 kg or more at 40 mg and 50 mg twice daily, which carries a PDUFA date of 24 October 2026 after a January 2026 complete response letter that asked for data on analytical methods for production batch testing. Joenja is approved in the US for patients aged 12 and over.

Access note

Two paediatric applications split by body weight and sequenced months apart tell you the January complete response concerned manufacturing analytics rather than clinical evidence. The 24 October date is the one that matters: if it clears, the lower-dose file becomes a formality on the same dataset.

  • Children are the patients APDS reaches first. The disease presents in childhood, so an adolescent and adult label strands the group where early treatment changes the course of lymphoproliferation and infection.
  • This extends the Week 33 launch story. OrphanPulse covered the Japanese launch for ages 4 and over in August; the US paediatric label is the larger commercial prize and still trails Japan.
  • Batch-testing complete responses are fixable and recurring. They cost less to resolve than efficacy questions, but they show CMC scrutiny on small-volume rare disease products is not easing.
08Regulatory · Stiff person syndromeAlso in NeuroPulse

Kedrion wins orphan status for its IVIG in stiff person syndrome, converting an off-label habit into a trial

Kedrion Biopharma announced on 22 September that FDA granted Orphan Drug designation to Qivigy, its 10% intravenous immune globulin, for stiff person syndrome. A Phase III double-blind, placebo-controlled study (NCT07552987) plans to enrol about 38 antibody-positive adults, randomised 1:1 to 2 g/kg every four weeks or placebo for 24 weeks, with an open-label extension. SPS has no FDA-approved treatment, and IVIG is already used off-label.

Regulatory note

Designation stacking usually finances early assets. Here it finances a label for a practice that already exists, and the seven years of US orphan exclusivity would protect Qivigy’s label, not IVIG as a class.

  • The trial is small and the endpoint undisclosed. Fluctuating stiffness makes SPS a hard indication to measure in 24 weeks.
  • A CAR-T competitor is ahead. Kyverna’s CD19 CAR-T ran a 25-patient registrational study on the timed 25-foot walk.
  • Plasma supply is the operational constraint. Every new IVIG indication draws on the same donor base as immunodeficiency patients.
09Regulatory · POLG diseaseAlso in NeuroPulse

Pretzel’s POLG activator adds Fast Track ahead of a first-in-patient Phase 2

Pretzel Therapeutics received FDA Fast Track designation for PX578 in POLG-mediated primary mitochondrial disorders, announced 22 September. FDA cleared the IND earlier in September for POLARIS, a randomised controlled Phase 2 in adults expected to start in late 2026. PX578 is a CNS-penetrant small molecule designed to activate mitochondrial DNA polymerase gamma. POLG disease has no approved disease-modifying therapy.

Regulatory note

Pretzel reports preclinical activity across the four most common POLG mutations, covering about 70% of patients. A single molecule that works across variants is the commercial case in a disease otherwise approached one mutation at a time.

  • No patient data exist yet. POLARIS is doing dose-finding and proof of concept together.
  • Mitochondrial DNA copy number is not an accepted surrogate. The primary endpoint choice will decide whether POLARIS can support registration.
  • Log the designation as positioning. Fast Track confirms unmet need and buys meetings, not evidence.
10Deal · Childhood nephrotic syndrome

Aclipse takes an option to buy Cypress and builds a childhood nephrotic syndrome franchise

Cypress BioPharma granted Aclipse Therapeutics an option to acquire the company, announced 22 September. Cypress brings CBP-002, in Phase II for childhood nephrotic syndrome, and CBP-228 at IND stage in cystinuria. On exercise, Aclipse adds Cypress’ renal development capabilities and expands parallel Phase II programmes for M-107 (lobeglitazone) in childhood nephrotic syndrome (LOKID) and gastroparesis (LOGAST). Aclipse is raising an undisclosed Series B. Terms were not disclosed.

Deal note

An option on a whole company is the cheapest way to hold two paediatric kidney programmes without committing money from a Series B that has not closed. The option and the financing are effectively one transaction, and whichever lands first will decide the other.

  • Childhood nephrotic syndrome is a steroid problem. Most children respond to corticosteroids; the unmet need is the relapsing and steroid-dependent group exposed to repeated courses. Ask which subgroup LOKID enrols.
  • Lobeglitazone is a repurposed diabetes drug. It is a thiazolidinedione approved in South Korea, and repurposing a PPAR gamma agonist for podocyte protection is plausible and cheap to develop.
  • Cystinuria is the stray. An IND-stage kidney stone disease sits oddly beside two Phase II nephrotic programmes and is the likeliest asset to be deprioritised.
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