Nanobiotix soars as late-phase cancer trial hits endpoint

A phase 2/3 trial of Nanobiotix’s NBTXR3 in soft tissue sarcoma has met (PDF) its primary endpoint. The top-line success against the pathological complete response rate endpoint sent Nanobiotix’s stock up by more than 50%.

NBTXR3 consists of crystalline nanoparticles designed to enhance the efficacy of radiation therapy. By administering intratumoral injections of the nanoparticles prior to external beam radiation therapy, Nanobiotix thinks it can dial up the antitumor effect, thereby better preparing the patient for surgical resection.

To test the idea, Nanobiotix enrolled 180 soft tissue sarcoma patients and randomized them to receive radiation therapy with or without NBTXR3 before undergoing surgery. 

The trial just met its primary endpoint. In the NBTXR3 arm, 16% of patients experienced pathological complete responses, meaning their resected tumors had at most 5% viable cancer cells. Just under 8% of patients in the control arm experienced such a response, resulting in the clinical trial hitting its primary endpoint with a p value of 0.0448. As the primary endpoint analysis required tumor samples, Nanobiotix only included the 162 patients who underwent resection in its calculation. The full population included 180 patients.

The tight squeeze under the 0.05 bar of statistical significance leaves scope for skeptical readings of the data, as do other aspects of the top-line information shared—and not shared—by Nanobiotix.

Nanobiotix is also yet to share data on some secondary endpoints relevant to the prospects of NBTXR3. The press release disclosing the data stated the trial met a secondary endpoint that looked at resection margins, but lacked details about the effect of NBTXR3 on tumor volumes or the objective response rate.

Those details will influence the prospects of NBTXR3 and the patients who take the nanoparticles but their absence did little to discourage investors, many of whom see the data as a big boost to NBTXR3 as it advances in other indications and potentially starts generating sales. 

Nanobiotix looks likely to rack up the first of those sales in Europe, where it plans to bring NBTXR3 to market via the CE mark process. A U.S. filing looked more distant but some observers think the soft tissue sarcoma data could enable Nanobiotix to accelerate its plans. 

"These results could potentially lead to an expedited U.S. filing as a drug for accelerated approval vs. our base case 2022E U.S. launch," Jefferies analyst Peter Welford wrote in a note to investors.

Welford thinks sales of NBTXR3 in soft tissue sarcoma will top out at $175 million. Other indications represent bigger opportunities. Head and neck cancer could be worth $550 million a year, according to Welford, while wider use may turn NBTXR3 into a blockbuster.