CarThera After the EIC Accelerator: Brain Implant Still in Trials

Glioblastoma kills 85% of patients within two years, according to the EU training network GLIOTRAIN, and one reason is plumbing: the blood-brain barrier keeps most chemotherapy drugs out of the brain tissue where the tumour regrows. Carthera, a 2010 spin-off of the Paris hospital group AP-HP and Sorbonne University, implants a grid of small ultrasound emitters in the skull that, switched on for a few minutes, loosens that barrier for several hours so that more of a drug gets through. In the EIC Accelerator pilot's March 2020 cut-off the European Commission selected its project DOMEUS for blended finance, according to the Commission's list of selected companies, which names Carthera as the project's only company. CORDIS records an EU grant of €2,064,325 towards a total cost of €2,995,353.50, from 1 October 2020 to 30 September 2022.

The project's stated aim was to run a pivotal phase 2b/3 trial, industrialise the implant and "prepare for international market introduction in 2023". Six years after the award, Carthera is alive, funded and in the middle of the largest trial yet of its kind. It has no approved product, and its filed accounts report no turnover for 2024 or 2025.

Where Carthera Stands Now

Carthera is an active company with no insolvency proceedings on record. The official French company register lists it as active, with its head office at 1 place Václav Havel in Lyon, according to the government company search service. Its legal notices in the BODACC show the move to that address in May 2023, after the registered office had moved from the Pitié-Salpêtrière hospital in Paris to Lyon in November 2021. The company's press releases of December 2023 and April 2025 place its US subsidiary in Boston, while its About page says New York. The latest notices are a capital increase published in October 2025, which raised the share capital to €128,912.50, and the filing of the 2025 accounts in July 2026.

The work itself is one trial. SONOBIRD compares the SonoCloud-9 implant combined with the chemotherapy drug carboplatin against standard treatment (lomustine or temozolomide) in patients with a first recurrence of glioblastoma, with overall survival as the main measure. ClinicalTrials.gov lists it as recruiting, with an actual start date of 29 January 2024, 560 patients planned, 56 listed sites and an estimated completion date of 30 June 2028; the record was last updated on 5 October 2026. Carthera announced the first 100 patients enrolled in April 2025, when it said "nearly all 40 participating sites" were active. In February 2024 the company expected recruitment of all 560 patients to take two years; 100 patients after about 15 months was well behind that pace, and no later enrolment figure has been published.

The Technology: Opening the Barrier From Inside the Skull

The SonoCloud-9 sits in the opening in the skull left by tumour surgery, under the skin. Before each chemotherapy cycle, a needle connects it to an external control unit and its nine emitters send low-intensity pulsed ultrasound into the surrounding brain for a few minutes; the barrier stays open for several hours, according to the company's description. The competing approach, focused ultrasound guided by an MRI scanner from outside the head, takes "three to four hours" per session against "two to four minutes" for the implant, chief executive Frédéric Sottilini told Clinical Trials Arena. The trade-off is that the implant needs surgery, which is why SONOBIRD only enrols patients who are due for a second tumour operation anyway.

The evidence that it works mechanically is published. In a phase 1 trial at Northwestern University in Chicago with 17 patients, reported in Lancet Oncology in 2023, brain concentrations were 3.7 times higher for paclitaxel and 5.9 times higher for carboplatin in sonicated than in non-sonicated tissue. In Carthera's own phase 1/2 trial with carboplatin, published in Nature Communications in February 2024, 33 patients received 90 monthly sonications without dose-limiting toxicity. In the 12 patients who received carboplatin just before sonication, median overall survival was 14.0 months from surgery and 1-year survival 58%. Those are small, single-arm numbers. Whether the approach makes patients live longer than standard treatment is exactly what SONOBIRD has to show.

What DOMEUS Promised, and What CORDIS Shows

DOMEUS was a two-year project. CORDIS files it under the SME Instrument phase 2 funding scheme of Horizon 2020, which the Commission ran as the EIC Accelerator pilot from late 2019. The final periodic report lists what was done: ANSM in France and the FDA in the United States allowed an extension of the ongoing pilot trial to test a different treatment sequence, and its recruitment was completed; "all the SonoCloud-9 devices" for the pivotal trial were manufactured, with biocompatibility, chemistry and sterility tests completed; additional subcontractors were qualified and the manufacturing process "is being validated for the first commercial batch"; regulatory paths were agreed with a notified body and authorities in Europe and the US; and more patents were granted.

The pivotal trial itself did not start during the project. The first patients were enrolled in January 2024, 16 months after DOMEUS closed, according to the company's announcement and a report by Drug Delivery Business. The market introduction planned for 2023 has not happened: Carthera's April 2025 release still describes SonoCloud as an investigational product without EMA or FDA approval, and no CE marking or US approval has been announced since.

1. Manufacture devices for the pivotal trialDeliveredAll SonoCloud-9 trial devices built and tested, per the CORDIS report.
2. Run a pivotal phase 2b/3 trialLateSONOBIRD started in January 2024, after the project; completion estimated for 2028.
3. Industrialise the implantPartialSubcontractors qualified; first commercial batch still "being validated" at project end.
4. International market introduction in 2023Not achievedNo CE marking or FDA approval announced by October 2026.
5. Become a commercial-stage companyNot achievedTurnover reported as zero for 2024 and 2025.

Judged fairly, a two-year grant could not have delivered a survival trial in glioblastoma, and the device work it paid for fed directly into SONOBIRD. But the commercial timetable written into the proposal was off by at least five years.

What Carthera Has Achieved Since the Award

The regulatory record is the strongest part. The FDA gave SonoCloud-9 Breakthrough Device designation in June 2022, and an end-of-phase-2 meeting in March 2023 brought what Carthera called FDA support for the phase 3 design. In May 2024 the FDA and the EMA granted orphan drug designation for carboplatin in malignant glioma, and in July 2024 France's health authority HAS gave a positive opinion on paying for the devices used at French SONOBIRD sites under its Forfait Innovation scheme, which the company says only 18 medical devices have entered since 2009. In July 2025 an EMA expert panel agreed that SonoCloud can be considered an orphan medical device, under a pilot that EMA opened in August 2024 for devices treating rare conditions affecting fewer than 12,000 people a year in the EU, as Walder Wyss summarised it.

Partnerships so far are for supply and research, not sales. Accord Healthcare agreed in November 2023 to supply carboplatin for the trials and a later launch, on undisclosed terms. Carthera also takes part, without EU funding of its own, in two EU training networks on glioblastoma, GLIOTRAIN and GLIORESOLVE, and its technology is named in SonoMYC, a 2025 ERC proof-of-concept grant to a Barcelona institute that wants to combine it with the cancer drug candidate Omomyc.

The Money

The EIC's own equity is the least transparent part of the record. In September 2020 Carthera announced that it would receive a "€2 million" grant and "€10.5M in equity" from the EIC, and that a Series C round was planned for early 2021. That round never appeared under that name. Instead, in June 2023 Carthera closed a €37.5 million round it called Series B, led by an undisclosed investor together with the EIC Fund and its existing investors Panakès Partners, Relyens Innovation Santé and Supernova Invest; the law firm Linklaters advised the EIC Fund on it, Le Monde du Droit reported, without giving the Fund's amount. In December 2023 an extra €4.5 million from the Texas-based Unorthodox Ventures and existing shareholders took the round to €42 million. The 2020 release had also called a €10 million round of December 2018 "Series B", so the company has used the label twice. Carthera is listed in the EIC Fund's portfolio, which confirms the equity was invested; whether the Fund put in the full €10.5 million, and when, is not public.

The accounts show where that money goes. Turnover never exceeded €71,611 in any year from 2019 to 2023 and was reported as zero for 2024 and 2025, while the net loss rose from €3.10 million in 2022 to €6.18 million in 2023, €9.31 million in 2024 and €12.56 million in 2025, according to the INPI financial ratios drawn from its filed accounts. The 2024 and 2025 accounts were filed with a confidentiality declaration, so the balance sheet and cash position are not public. Staff numbers also disagree: the company's website says 29 full-time specialists, while the register places it in the 10 to 19 employee bracket for 2024.

Why Europe Should Care

Brain cancer is a field where drugs exist but cannot reach the tissue where they are needed. Europe's Beating Cancer Plan, a €4 billion political commitment, covers diagnosis and treatment as well as prevention, and a European device that lets an established chemotherapy such as carboplatin work in the brain falls squarely within it. Carthera is also an early test of the EU's newer regulatory routes for rare diseases: SonoCloud was, by the company's account, one of the first projects selected for EMA's orphan medical device pilot.

The competing method named by Carthera itself is external focused ultrasound guided by MRI, which needs hours per session rather than minutes, according to the chief executive's comparison in Clinical Trials Arena. Carthera describes SONOBIRD as the world's first randomised, multicentre pivotal trial of barrier opening before chemotherapy in recurrent glioblastoma. If it shows a survival benefit, Carthera would have the first such evidence; the result is not due before 2028.

The Verdict

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