Hopstem maps course to bring stem cell stroke therapy to US

China's Hopstem Biotech has been cleared to start clinical trials of a stem cell-based therapy for ischaemic stroke in the US, following negotiations with the FDA.

The company's therapy, codenamed hNPC01, is based on induced pluripotent stem cells (iPSCs) and is being developed to treat the motor disability that can follow a stroke, mainly by stimulating the release of factors that enhance natural repair mechanisms in the brain, but also by replacing damaged neurons.

Hopstem has already completed phase 1 testing of hNPC01 in China, with encouraging results, and says it has now reached agreement with the FDA on an "accelerated clinical development pathway" in the US that will involve a bridging phase 2 study in US patients.

In December, the FDA also awarded fast-track status to hNPC01 as a therapy that could transform the treatment of ischaemic stroke. At the moment, the only approved therapies are thrombolytic drugs, delivered within the first few hours of symptom onset, to break up the blood clots that block the supply of blood to affected areas of the brain.

Clinical data shows that approximately 50%–70% of stroke patients suffer from varying degrees of motor dysfunction that can affect daily-living activities, with only about 5% of them achieving full recovery.

While the potential of using stem cells to treat stroke has been discussed for years, Hopstem says that hNPC01 is currently the furthest along in clinical development, adding that the FDA agreement "will significantly shorten the product's time-to-market."

In its phase 1 trial, which involved 23 patients who had suffered a stroke between six months and five years previously, Hopstem found that treatment with the stem cells implanted into the brain was associated with sustained improvements in motor function over 18 months of follow-up.

Among patients with two years of follow-up, there are signs of a plateauing of the effect without any decline in efficacy. Meanwhile, there was no evidence of dose-limiting toxicity or the formation of tumours, which is a perennial concern when dealing with stem cell therapies.

According to Hopstem, which was founded by Johns Hopkins University researchers and also has a presence in the US, the FDA will allow the company to bypass phase 1 testing in the US and move straight to phase 2 with an adaptive trial design, which means it can be directly expanded into a phase 2/3 pivotal trial.

"The FDA's endorsement of core protocol elements, including patient population, dose selection, clinical endpoint settings, statistical plan, without raising any safety concerns, has cleared critical obstacles for the efficient advancement of subsequent international multicentre studies," commented the biotech's head of medical affairs, Dr Shuning Zhang.

Companies currently working on stem cell therapies for ischaemic stroke include Japan's SanBio, while others that had programmes in this area, notably Athersys and Stemedica Cell Technologies of the US, have run into financial difficulties that have stalled their programmes.