Six patients treated with 2-bromo-LSD, a nonhallucinogenic analog of LSD, showed a significant reduction in cluster headaches per day; some were free of the attacks for weeks or months, according to a presentation by Harvard Medical School and Hannover Medical School researchers.

2-bromo-LSD (BOL) was developed by Sandoz, the Swiss company that discovered the psychedelic effects of LSD.

The researchers have founded Entheogen Corp. to fund further research and are hoping to start a phase II clinical trial with 50 patients later this year.