Exactmer and the EIC Accelerator: Liquid-Phase Oligo Membranes

Oligonucleotide drugs are built one nucleotide at a time, and the standard way to do it, on a solid support, suffers from "low batch sizes, high production costs, environmental concerns", in the words of the EU project summary for the company profiled here. Exactmer, a 2017 spin-out of Andrew Livingston's laboratory at Imperial College London, proposes to do the whole synthesis in solution instead, attaching the growing chains to a branched hub molecule and washing away excess reagents through a membrane after every step. It calls the method Nanostar Sieving.

The European Innovation Council selected Exactmer's project, OPToligo, at its October 2025 cut-off for a grant without equity. The company appears in the EIC's list of selected companies published with its 17 February 2026 announcement of 61 winners, and CORDIS records an EU contribution of €2,499,999 for a project signed on 28 April 2026 and running from 1 May 2026 to 30 April 2028. Six months in, the project is too young to judge on results. What can be checked is the science behind it, the claims made for it, and the company's balance sheet.

How Nanostar Sieving differs from solid-phase synthesis

In solid-phase synthesis the growing oligonucleotide is anchored to beads, and every coupling step is followed by a wash that carries reagents away. The CORDIS summary links this method to low batch sizes. Exactmer's website describes the alternative: chains grow on a multi-branched hub in solution, and after each step an organic solvent nanofiltration membrane holds back the large hub-and-chain molecule while the smaller excess building blocks pass through. The company sells three membrane lines built around that idea: Exact-10 for synthesis, Exact-01 for recycling solvent without distillation, and Exact-20 for concentration and solvent exchange. The site lists oligonucleotide types from antisense to siRNA as applications, with peptides, linkers for antibody-drug conjugates and single-length PEGs in development, and shows an ISO 9001 certificate.

The technical claim has a peer-reviewed anchor. In December 2025 Organic Process Research and Development published "Fully Liquid Phase Oligonucleotide Synthesis", with 42 authors and Livingston as senior author. The company's summary says the work made a 21-mer siRNA strand and a 16-mer antisense-type gapmer with the oligo kept in a single solvent from coupling to isolation, and that co-authors came from AstraZeneca, Alnylam, Novartis and CPI. The full paper was not accessible for this review, so its batch size, purity and yield figures are not reported here.

What OPToligo promises, and two versions of the target

CORDIS describes OPToligo as an effort to improve the Nanostar process for large batches, develop the membranes and lower manufacturing cost. Its summary names three targets: batches of more than 50 kg or more than 5 mol, manufacturing costs up to 35% lower than traditional methods, and up to 60% less solvent through a membrane-based recycling loop.

Exactmer's own release of 19 February 2026 describes the same 24-month project, which it spells OptOligo, in smaller terms: batch production of up to 200 mmol, about 1 kg, reagent use below 1.2 equivalents for a cost and waste reduction of about 33% against solid-phase synthesis, and the same 60% solvent figure. The release also says the work will prepare the platform for GMP use at customer sites. The two documents differ on batch size by a factor of at least 25. Neither explains the gap, and it is not public which figure the grant agreement's milestones use.

The market case in the release is that at least six oligonucleotide medicines expected by 2030 will each need about 500 kg a year, against global capacity of about 200 kg a year for such drugs. Those are the company's figures, and no independent source for them is cited in the release.

1. Fully liquid-phase synthesis of a therapeutic-length oligoPublished21-mer siRNA and 16-mer gapmer in the December 2025 OPRD paper, before the project began.
2. Batches above 50 kg or 5 mol (CORDIS)Not yet shownNo batch of this size reported; the company's own target is 200 mmol.
3. Up to 35% lower manufacturing costClaimNo cost comparison published.
4. Up to 60% less solvent through recyclingClaimExact-01 recycling membrane is listed for sale; no measured reduction at scale published.
5. GMP-ready process at customer sitesToo earlyNo customer installation announced; CORDIS shows no report yet.

A long run of public grants

OPToligo is not Exactmer's first EIC money. A CORDIS search for the company returns two projects: OPToligo and NANOLIGO, a €150,000 European Research Council proof-of-concept grant that ran from September 2020 to February 2022 with Exactmer as sole beneficiary. In February 2023 the company announced €2.49 million from the EIC Transition programme for ALTOLIGO, a project on alternative oligo chemistries that it said was financed in the UK through UKRI's Horizon Europe guarantee; no ALTOLIGO record appears in CORDIS, which is consistent with that route but does not confirm it.

The company's news page lists Innovate UK SMART grants in 2020 and 2022, a Knowledge Transfer Partnership with Queen Mary University of London in 2022 and a FASST grant in 2024. Imperial College reported in February 2021 that Exactmer would lead the first phase of a CPI project on oligonucleotide manufacturing with AstraZeneca, Novartis and UKRI. In March 2026 Exactmer said it would lead a 36-month Innovate UK project worth more than £7 million in total on bio-based solvents for medicine manufacturing, with GSK, Croda, Cytiva and CPI among the partners; its own share is not stated.

The one commercial investor the company has named is Asahi Kasei. In August 2024 Exactmer announced a partnership with Asahi Kasei Bioprocess, which would use Exactmer's technology to build equipment, and an investment by Asahi Kasei Medical. No amount or form was given, and web searches on 4 November 2026 found no announcement of the investment from Asahi Kasei itself. The filed accounts show the share capital unchanged at £301 from 2021 to 2025.

What the accounts show

Exactmer files abridged small-company accounts at Companies House without an income statement, so revenue and the annual result are not public. The balance sheets are. Net assets rose from £1.23 million at the end of 2021 to £3.49 million at the end of 2023, then fell to £3.06 million in 2024 and £2.00 million in 2025. Retained earnings fell by £428,054 in 2024 and by £1,062,632 in 2025, while the share capital and share premium did not change. Cash at the end of 2025 was £1,528,505.

The 2025 accounts, approved on 17 September 2026, state that the company has been financed by equity, grants, revenue and a £1.25 million working capital loan. They record a convertible loan note to a third party of £1,343,377 including interest, unsecured, at 5%, maturing on 23 July 2027, which the company may convert into shares at maturity. The directors write that they expect to conclude a fundraise within nine months and are in discussions with the noteholder to extend the repayment backstop beyond July 2027. Other debtors include £978,657 of research and development tax credits due from HM Revenue and Customs. Trade debtors were £25,674, down from £108,500 a year earlier. The accounts also note that the three-year lease on the operating premises ended on 17 April 2026, with renewal under negotiation.

The filing history shows the register moving since. Share allotments were filed for 27 April, 4 June, 16 October and 23 October 2026, raising the nominal capital from £301 to £305.406; the price paid for the new shares is not shown on the register. Piers Gaffney, a director since incorporation and the first author of the 2025 paper, left the board on 30 May 2026; Cristina Bertulli joined it on 26 May 2026. The registered office moved from Harrogate to Oxford Science Park in July 2026.

A membrane company with more than one market

The same membrane chemistry is being pointed elsewhere. In June 2026 The Chemical Engineer and Queen Mary University of London reported a paper in Science on ultrathin membranes that fractionate crude oil without heat, made 1 m wide on a roll-to-roll line and run on real crude for 30 days. Livingston, now also at Queen Mary, led the work, and The Chemical Engineer names Exactmer's head of membrane development, Zhiwei Jiang, among the team. The bio-based solvents project announced in March 2026 is a third line of work. None of these changes the status of OPToligo, but they show a company whose membranes are its product, with oligonucleotides as the largest stated application.

Why the EU funds it

Exactmer is a UK company funded under Horizon Europe. The policy case for oligonucleotide manufacturing capacity sits in the Critical Medicines Act the Commission proposed on 11 March 2025, which the European Parliament's summary describes as aimed at diversifying supply chains and strengthening manufacturing in the EU. A process that lets drug makers build oligonucleotides in larger batches with less solvent would serve that goal wherever it is licensed. CORDIS tags OPToligo at 40% for climate action.

Exactmer has not been asked for comment. The reporting is based on publicly available sources, listed below.