Back in 2021, the Lyme community was buzzing about a potential new treatment called hygromycin A. It came out of Dr. Kim Lewis’s lab at Northeastern University, and the early news sounded genuinely thrilling.

Here was a compound that demonstrated selective killing against Borrelia, the Lyme pathogen, without harming the beneficial microbes in the gut. That’s important, because gut disruption has long been one of the biggest drawbacks of antibiotic treatment for Lyme.

Early studies looked promising. Hygromycin A cleared Lyme infection in lab mice, left their gut bacteria intact, and even showed potential for reducing Lyme in reservoir animals like field mice. With results like that, the next logical step was to see whether the compound could be developed into a treatment for people.

That’s where Flightpath Biosciences came in. The company licensed hygromycin A and began developing it into a drug known as FP100. Working closely with Dr. Lewis, Flightpath manufactured the compound, completed the required animal studies, and moved it into human testing. Phase 1 clinical trials began in 2024.

Recently, Flightpath CEO Matt Tindall shared an update on what the company learned from those trials—and the news wasn’t immediately what many Lyme patients had hoped for.

Hard lessons

“We learned hard but crucial lessons,” Tindall wrote in a letter to the Lyme community. “FP100 showed limited oral bioavailability in humans, meaning too little of the drug reached the bloodstream and tissues at levels needed for robust, reliable clinical benefit.”

In simpler terms: the medicine couldn’t consistently get to where it needed to go in the body for a long-enough duration, in an oral dosage form, to effectively treat Lyme disease.

Because of that, Flightpath is now going in a different direction. Still collaborating with Dr. Lewis, the team has shifted its focus to a new drug candidate named FP530 (forazemin).

According to Tindall, early findings suggest that FP530 clears Lyme pathogens in animal models, may circulate more effectively throughout the body, and potentially do so without impairing healthy gut bacteria.  The company describes it as an even more promising drug candidate for patients with Lyme disease, though some supporting details have not yet been made public.

The good news is that FP530 is not far behind FP100 in development, and the company plans to begin a clinical trial later this year.

The bottom line? Creating a new Lyme drug is tough—probably tougher than many of us realize. But Flightpath Biosciences intends to keep at it. The company’s decision to pivot rather than give up reflects a commitment to getting this right.

And that’s cause for optimism in the Lyme community. Stay tuned for further developments.

TOUCHED BY LYME is written by Dorothy Kupcha Leland, President of LymeDisease.org. She is co-author of Finding Resilience: A Teen’s Journey Through Lyme Disease and of When Your Child Has Lyme Disease: A Parent’s Survival Guide. Contact her at dleland@lymedisease.org.