Arrowhead Wins UK Nod for Rare-Disease Drug Redemplo

Arrowhead Pharmaceuticals has won UK marketing authorisation for Redemplo (plozasiran), its small-interfering-RNA drug for the rare lipid disorder familial chylomicronaemia syndrome. The Medicines and Healthcare products Regulatory Agency granted the licence to Arrowhead's Irish subsidiary on 19 October 2026, using its International Recognition Procedure to lean on the European Medicines Agency's earlier review rather than starting from scratch.

Redemplo's GB authorization, in four figures

5regulatory markets now authorising Redemplo (US, Canada, Australia, EU, GB)

~80%median triglyceride reduction at month 10, 25 mg arm, vs. 17% placebo

25mgsubcutaneous dose, injected once every three months

75adults enrolled in the pivotal PALISADE trial

Figures from the MHRA's 19 October 2026 authorisation notice and Arrowhead's PALISADE Phase 3 results, presented at ESC Congress 2024 and published in the New England Journal of Medicine.

From a Pasadena incubator to one approved drug

Redemplo's five-market march

1. 2007

   Anzalone takes over, pivots to RNAi

   Christopher Anzalone becomes CEO of what was then a diversified holding company and begins narrowing it around an RNA-interference subsidiary, Calando Pharmaceuticals.

2. 2011

   Builds out RNAi intellectual property

   Arrowhead acquires Roche's RNAi assets, among other deals, assembling the chemistry and delivery patents behind its TRiM platform.

3. September 2024

   PALISADE Phase 3 reads out

   The pivotal trial meets its primary and key secondary endpoints; results are presented at the European Society of Cardiology Congress and published in the New England Journal of Medicine.

4. 18 November 2025

   FDA approval

   Redemplo becomes Arrowhead's first FDA-approved medicine, for adults with familial chylomicronaemia syndrome.

5. 5 January 2026

   Health Canada Notice of Compliance

   Canada becomes the second market to authorise Redemplo.

6. 1 May 2026

   Australia's TGA approves

   Redemplo is cleared in Australia, Arrowhead's third regulatory market.

7. 22 June 2026

   European Commission marketing authorisation

   The EU grants authorisation across its member states, which later becomes the reference decision for the UK's recognition route.

8. 19 October 2026

   MHRA authorises Redemplo in Great Britain

   The UK regulator grants a marketing authorisation via its International Recognition Procedure, referencing the EMA's decision.

Redemplo is the only drug Arrowhead Pharmaceuticals has ever brought to market. For most of its history the company was a diversified holding vehicle; Christopher Anzalone, recruited to run it in 2007, spent the years since narrowing it around a single bet on RNA interference — using short interfering RNA (siRNA) molecules to silence the gene instructions behind a disease rather than blocking the resulting protein after the fact. That bet produced Arrowhead's TRiM delivery platform and, eventually, plozasiran.

What the MHRA actually signed off on

Familial chylomicronaemia syndrome is a rare genetic disorder in which the body cannot clear chylomicrons — large, fat-carrying particles — from the blood, pushing triglyceride levels routinely above 1,000 mg/dL and raising the risk of acute pancreatitis, a painful and potentially life-threatening inflammation of the pancreas. Plozasiran works by silencing the liver's production of apolipoprotein C-III (APOC3), a protein that normally slows the breakdown of fats; with less APOC3 circulating, the body clears triglycerides far faster.

“REDEMPLO's approval is a transformational milestone for Arrowhead.” Christopher Anzalone, President and Chief Executive Officer, Arrowhead Pharmaceuticals — 18 November 2025, on the drug's original FDA approval

The MHRA's own notice lays out the evidence behind both that original approval and Tuesday's GB authorisation: in the 75-patient PALISADE trial, patients randomised to 25 mg or 50 mg plozasiran every three months saw a median fasting-triglyceride reduction of roughly 80% and 78% respectively at month 10, against 17% for placebo, alongside fewer acute pancreatitis episodes in the treated groups. The most common side effect was hyperglycaemia, reported in more than 1 in 10 patients; headache, nausea and injection-site reactions were also common. The authorisation itself followed the MHRA's International Recognition Procedure, Route B — a post-Brexit pathway that lets the UK regulator lean on a trusted reference regulator's decision, here the EMA's June 2026 authorisation, rather than re-running a full independent review.

Already outnumbered on the shelf it's entering

Redemplo is not the first drug approved for familial chylomicronaemia syndrome in Europe, and it will not be the first in Great Britain either. Sobi's volanesorsen (Waylivra) held that distinction for years as the sole approved FCS therapy; Ionis Pharmaceuticals' olezarsen (Tryngolza), commercialised outside North America by Sobi, won EU marketing authorisation in September 2025 on the strength of its Phase 3 Balance study. Both rivals are antisense oligonucleotides, a related but chemically distinct class from Arrowhead's siRNA approach — the distinction RA teams will need to track as prescribing patterns in Great Britain settle.

Three things Redemplo is betting on in a crowded niche

01

Only siRNA on the shelf

Waylivra and Tryngolza both work by blocking APOC3 messenger RNA with antisense chemistry; plozasiran instead triggers RNA interference to degrade it, Arrowhead's signature mechanism across its pipeline.

02

Quarterly dosing

A 25 mg injection every three months is a materially lighter treatment burden than more frequent regimens, in a patient population already managing a restrictive low-fat diet.

03

Five-market reach, fast

Less than a year after its first approval, Redemplo is now authorised across North America, Oceania and Europe including Great Britain — a faster rollout than many rare-disease drugs manage in their first five years.

A market sized in the tens of millions, not billions

Familial chylomicronaemia syndrome is vanishingly rare — published literature estimates put true FCS prevalence at roughly one to two people per million, though a related and far more common condition, multifactorial chylomicronaemia syndrome, affects closer to one in 12,000. That scarcity shapes how analysts size the category: commercial forecasters differ sharply on scope and method, but one such estimate puts the global FCS drug market at $642.5 million in 2024, rising to $1.16 billion by 2033.

What a five-market authorisation is worth

$642.5M → $1,161.5M

Global familial chylomicronaemia syndrome (FCS) drug market, 2024 to 2033, as forecast by SkyQuest Technology Consulting.

2024$642.5M

2025$686.2M

2033$1,161.5M

Sources: SkyQuest Technology Consulting, Familial Chylomicronemia Syndrome Market report

Regulatory News outlook

We expect Redemplo's GB authorisation to add a small, slow-growing slice of patients rather than meaningfully reshape the category's size, since Great Britain's share of global FCS prevalence — a disease measured in people per million — is itself a few hundred patients at most.

How we got here: Applying the UK's roughly 1.3% share of global population to SkyQuest's $1,161.5 million 2033 global forecast implies a UK FCS drug opportunity in the low tens of millions of dollars by 2033, before accounting for how the market splits between Redemplo, Tryngolza and Waylivra.

Redemplo against the FCS shelf it joins in Great Britain

Product	Mechanism	Dosing	GB/EU status
Redemplo (plozasiran) — Arrowhead	siRNA, silences APOC3 mRNA	25mg subcutaneous, every 3 months	MHRA authorised 19 Oct 2026; EU authorised Jun 2026
Tryngolza (olezarsen) — Ionis / Sobi	Antisense oligonucleotide, targets APOC3 mRNA	Monthly subcutaneous injection	EU authorised Sep 2025
Waylivra (volanesorsen) — Sobi	Antisense oligonucleotide, targets APOC3 mRNA	Weekly subcutaneous injection (loading), then less frequent	EU authorised since 2019, long-standing UK availability

From each company's own labelling and regulatory announcements; not a clinical comparison. Relative dosing frequency and years on market, not head-to-head trial data, distinguish the three today.

What a GB licence does not settle

• Pricing and reimbursement: an MHRA marketing authorisation permits a medicine to be sold in Great Britain; it is a separate step for NICE or NHS commissioners to agree a price and funding route, which this authorisation does not itself resolve.
• Launch timing: Arrowhead has said only that it expects to launch independently in the UK following European approval; this article found no confirmed GB launch date or pricing announcement.
• Head-to-head data: no published trial compares plozasiran directly against olezarsen or volanesorsen in FCS patients; the comparison above rests on each company's own labelling, not clinical evidence of one working better than another.
• Patient numbers: because FCS is defined down to the single-digit-per-million level, even optimistic uptake projections translate to a few hundred patients across all of Great Britain, not a large commercial population.

Frequently asked questions

What exactly did the MHRA authorize on 19 October 2026?

A Great Britain marketing authorisation for plozasiran (Redemplo) for adults with familial chylomicronaemia syndrome (FCS), as an adjunct to a low-fat diet to reduce triglycerides. The licence was granted to Arrowhead Pharmaceuticals Ireland Limited through the MHRA's International Recognition Procedure, Route B, using the European Medicines Agency as the reference regulator.

Is this Redemplo's first approval anywhere?

No. The FDA approved Redemplo on 18 November 2025 as Arrowhead's first commercial drug. The European Commission granted EU-wide marketing authorization on 22 June 2026, Australia's TGA approved it around 1 May 2026, and Health Canada issued a Notice of Compliance on 5 January 2026. The MHRA authorization extends that same drug to Great Britain specifically, since UK licensing runs separately from the EU's since Brexit.

How is Redemplo dosed, and what did the trial show?

It is a 25 mg subcutaneous injection given once every three months alongside a low-fat diet; patients or trained caregivers can administer it themselves. In the pivotal 75-patient PALISADE trial, the median triglyceride reduction at month 10 was about 80% in the 25 mg arm versus 17% on placebo, with fewer acute pancreatitis events in the treated group.

Does Redemplo have the FCS market to itself?

No. Ionis Pharmaceuticals' olezarsen (Tryngolza, marketed outside the US by Sobi) was approved in the EU in September 2025 and already competes for the same small patient population; Sobi's older volanesorsen (Waylivra) remains available too. Redemplo is the only siRNA medicine among them; the others are antisense oligonucleotides.