Maryland-based migraine devices maker eNeura is closing in on a $6.6 million funding round, with $5.8 million raised so far.

The company has sold equity to 67 investors so far in a round launched on Aug. 18, 2014, according to an SEC report filed last week. There’s no minimum investment for outside investors, according to the report.

eNeura’s device is the 1st of its kind to use transcranial magnetic stimulation to depolarize neurons on the brain, a process that doctors believe may interrupt migraine activity. Designed for home use, patients place the device against the back of the head, where a magnetic pulse targets the occipital lobe.

The device won FDA approval in May with positive results from eNeura’s double-blind, placebo-controlled studies in more than 200 patients, which found that nearly 38% of eTMS patients were pain-free 2 hours after using the device, compared with only 17% of patients in the control group. About 34% of eTMS patients were pain-free after 24 hours, compared with 10% of the control patients. Researchers reported no device-related serious adverse events.