EIC Accelerator Check: Orthox and Its Silk Cartilage Implant

For more than a decade, Orthox tried to repair worn knee cartilage with an implant made from purified silk protein. The Oxford University spin-out was selected in the European Innovation Council's October 2019 round and signed a Horizon 2020 grant of €2,496,960.38 towards a €3,567,086.25 project to take its FibroFix Cartilage implant through clinical trials, according to CORDIS. It went on to raise a $12.5 million Series A for a 75-patient study. Two patients were treated. Both had the implant surgically removed on 5 May 2023, and the trial was terminated, according to the sponsor's study summary on ISRCTN and the ClinicalTrials.gov record, which gives the reason as "Safety issues".

The company still exists. Since 22 August 2025 the operating company has been called Bounce Biomedical Limited, according to Companies House, and its new website describes a different product built on a different material, licensed from Imperial College London.

Where the Company Stands Now

Orthox has not been wound up, and no insolvency notice for it appears in The Gazette. Its parent, Orthox Holdings Limited, filed group accounts for the year to 28 February 2026 in June 2026, according to its Companies House filing history. The accounts describe a company that has cut back hard. "Following adverse clinical results on the FFLEX trial in 2023, the subsequent cost rationalisation process has continued to reduce company expenditure significantly," the directors write. With a new £100,000 Innovate UK grant awarded in 2026, they forecast that funds will last "to at least the end of Q3 2027", and the Wellcome Trust has confirmed by letter that it will not call in its loan before June 2028. The auditor's report flags a material uncertainty over the company's ability to continue as a going concern.

The silk implant is no longer the plan. The same accounts say the directors are pursuing "alternative product development opportunities" from intellectual property licensed from Imperial College London, backed by an Innovate UK Knowledge Transfer Partnership with the university. Bounce Biomedical, which gives the same Milton Park address and telephone number on its contact page as Orthox, presents ChondroBounce, a 3D-printed implant for damaged cartilage and the bone beneath it, made from "Bouncy Bioglass", a silica and polymer hybrid invented by Julian Jones's group at Imperial. Imperial announced that material in 2016, when its researchers predicted it would take about ten years to reach the market. Bounce's team page lists Nick Skaer as chief executive and Jones and two Imperial researchers as co-founders. No clinical trial, regulatory filing or investment for ChondroBounce has been announced. The old Orthox website is still online, still presents FibroFix as the lead product and carries no news after July 2022.

The Technology: Silk That Behaves Like Cartilage

Cartilage covers the ends of the bones in the knee and barely heals. Damage often progresses to osteoarthritis, which CORDIS says affects more than 500 million people. Surgeons can trim damaged tissue, transplant cartilage or, in the end, replace the joint. FibroFix was meant to sit between those options: a porous scaffold of fibroin, a protein extracted from silk, that would bear load like cartilage from the day of surgery while the body's own cells grew into it. Orthox argued that this needed no expensive cells or biologics and, in its EIC proposal, that it was "up to 10 times less expensive than other solutions", a claim CORDIS repeats without supporting figures. The material came out of Oxford University, according to the University of Bristol, whose researchers ran the trial.

Orthox's patent position was real: in July 2022 it said patents from its implantable tissue repair family had been granted in the US, China, the UK, Germany and France, according to its press release. Whether the implant worked in people was the open question the EIC project was meant to answer.

What the EIC Project Promised, and What CORDIS Shows

The European Commission's list of companies selected in the 9 October 2019 EIC Accelerator pilot cut-off names Orthox Limited alone for FibroFix Cartilage, with no partner company, and marks the award as blended finance, a grant plus EIC equity. CORDIS records only the grant, signed on 17 March 2020 for a project from 1 July 2020 to 31 October 2023. Orthox appears under neither name on any of the 16 pages of the EIC Fund's list of invested companies, checked for this article. No source found for this article shows that the equity part was ever invested. The award followed a €50,000 Horizon 2020 phase 1 feasibility study, also called FibroFix, that ran from January to April 2019, according to CORDIS.

The objective, in the words of the project's final periodic report, was "to clinically validate FibroFix through pivotal clinical trials, build manufacturing capability, and create the platform for post-project commercialisation". The report credits the first half of the project with a lot: preclinical tests that met the ISO 10993 biocompatibility standard, promising results in an animal model, certification to the ISO 13485 quality standard and GMP production, and a manufacturing scale-up sufficient for the trial.

1. Preclinical verification and validationDeliveredBiocompatibility, animal model and mechanical tests completed, per the CORDIS report.
2. Manufacturing capabilityDeliveredISO 13485 compliance, GMP production and scale-up for the trial, per CORDIS.
3. Private investment to continueDelivered$12.5M Series A closed in February 2022, per Penningtons Manches Cooper.
4. Clinical validation in a 75-patient trialNot achievedTwo patients treated; both implants removed; trial terminated for safety, per ClinicalTrials.gov.
5. Platform for commercialisationNot achievedNo CE mark or UK approval announced; the company has since moved to another material.

What Happened in the FFLEX Trial

The Series A, led by Parkwalk with Oxford Technology & Innovations EIS Fund, Perivoli Innovations and Additio Investment Group, was raised to run that trial, according to Orthox and OTW. The plan was six patients with six months of follow-up, then 75 in total at Southmead Hospital in Bristol and in Budapest. The UK regulator, the MHRA, cleared the study in July 2022, and the National Institute for Health and Care Research awarded nearly £1.2 million towards it, the University of Bristol said.

The sponsor's executive summary of the terminated study, filed on ISRCTN in September 2024, sets out what followed. Two patients received the implant at Southmead, on 2 December 2022 and 27 January 2023. The first developed swelling that did not settle; the second developed synovitis, inflammation and more pain than expected at three months. Both implants were removed in reoperations and both patients were withdrawn on 5 May 2023. Recruitment was halted, and after consulting its data monitoring committee the sponsor terminated the study on 14 June 2023. The summary concludes that the implant and its drill set "failed to demonstrate safety and performance for their intended purpose". A year after removal, neither patient had what the summary calls a "normal" knee: one was due for a partial knee replacement and the other for a bone graft to fill the defect left behind.

The Money

Orthox raised more than £21 million before the trial, by its own count in 2022, including £2.65 million in Wellcome Trust Translation Awards, £1.9 million from the NIHR i4i programme, a £1.7 million Biomedical Catalyst award from the UK innovation agency and the €2.5 million EIC grant, according to the University of Bristol and the company's Series A release. By February 2024 the group had written down £7.85 million of the £8.19 million of development costs it had capitalised, according to the group accounts for 2025 and 2026.

The balance sheet has shrunk to a small research operation. At 28 February 2026 the group held £1,340,178 in cash and had net liabilities of £1,595,404, against £506,245 two years earlier. Its long-term debt of £3,303,568 consists of £2,859,347 borrowed from the Wellcome Trust under convertible loans dating from 2009 and 2013, and a £444,221 convertible loan described as from "EIT"; the accounts print the Wellcome figure once as £2,895,347, but the two loans sum to the total only with £2,859,347. The deficit on the profit and loss reserve grew by £570,514 in the year to February 2025 and by £536,016 in the year to February 2026, to £11,273,544. Shares were issued in December 2024 and May 2025, but the 28,413 new shares of the latest year brought in £28.41, so they did not add funding.

Why Europe Should Care

Osteoarthritis is "second only to heart disease as a cause of work disability", the project's CORDIS summary says, and a cheap implant that delays knee replacement would matter to every health system that pays for joint surgery. The EU's Medical Device Regulation, applied since 26 May 2021, is built to "maintain a high level of safety, while supporting innovation", and the FFLEX study, run under it, did what a first-in-human study is for: it stopped the device after serious adverse events in its first two patients, before 73 more were treated. The case also shows how Brexit touched EIC projects. The CORDIS report says Orthox moved its Hungarian trial plans forward to limit the combined risk of Brexit and Covid-19. The UK has been associated with Horizon Europe since 1 January 2024, according to UKRO.

The Verdict

Orthox, now Bounce Biomedical, has not been asked for comment for this article. It is based entirely on public records, company statements, trial registries and EU project data, linked throughout.