Skyhawk’s drug trial takes flight in the US

On November 4, 2026, Skyhawk Therapeuticstherapeutics treatments announced that the first participants in the United States have now received treatment in FALCON-HD, a large international clinical trialclinical trial Very carefully planned experiments designed to answer specific questions about how a drug affects human beings designed to test whether this once-daily pill is safe and effective for people with HD. It’s an exciting step forward, particularly for the US HD community, but there’s still a long road ahead before we’ll know whether SKY-0515 can deliver on its promise.

Two targets, one pill

SKY-0515 takes an interesting approach to treating HD. Rather than targeting just one aspect of the disease, it reduces levels of two proteins involved in HD biology.

The first is expanded huntingtin, the harmful protein made in the cells of people who carry the expanded HD gene. Lowering this protein is a major focus of drug development, with several other treatments pursuing the same goal. The second is PMS1, a protein involved in DNA repair. PMS1 contributes to somatic instabilitysomatic expansion A process in which the CAG repeat in the Huntingtin gene can change over a person’s lifetime in some cells of the body, particularly in the brain., a process where the already-expanded CAG repeats in the huntingtin gene grow even longer in some cells over time. Increasing evidence suggests this process is important in driving HD progression.

SKY-0515 works by changing how cells process RNARNA the chemical, similar to DNA, that makes up the ‘message’ molecules that cells use as working copies of genes, when manufacturing proteins., the molecular instructions used to make proteins. Unlike some other huntingtin-lowering approaches that require spinal injections or brain surgery, SKY-0515 is taken as a pill once a day. 

Early clinical results have provided encouraging evidence that SKY-0515 can lower the levels of its intended targets. However, it is not yet clear if changing the levels of these proteins will improve symptoms or slow HD progression. That is what the Phase 2/3 FALCON-HD clinical trialclinical trial Very carefully planned experiments designed to answer specific questions about how a drug affects human beings is designed to work out. 

FALCON-HD spreads its wings

The FALCON-HD programme includes two large studies involving people with HD at ISS Stage 2, when tests can detect changes in movement or thinking, or Stage 3, when HD also starts to affect daily activities. The first, conducted in Australia and New Zealand, has completed enrolment with 144 participants. The second is a larger international study aiming to recruit 400 participants across more than 40 sites worldwide.

Skyhawk reports that approximately 250 participants have already enrolled across the global programme, with more than 50,000 doses of SKY-0515 administered to date. Now, the first US participants have received treatment at a clinical site in Colorado, with additional US centres expected to begin dosing in the coming weeks.

These studies are randomised, double-blind, and placebo-controlled. This means that participants are assigned at random to receive one of three doses of SKY-0515 or a placeboplacebo A placebo is a dummy medicine containing no active ingredients. The placebo effect is a psychological effect that causes people to feel better even if they’re taking a pill that doesn’t work., and neither participants nor investigators know which individuals are in which groups. This design hopes to determine whether any differences in disease progression are caused by the drug treatment rather than chance or other factors.

A milestone, not a finish line

The expansion of FALCON-HD into the US is welcome news. It reflects substantial progress in developing SKY-0515 and creates more opportunities for people with HD to contribute to research. But we need to be careful not to confuse trial progress with proof that a medicine works.

Although earlier findings in smaller groups of people are encouraging, SKY-0515 has not yet been proven to slow HD progression. The larger FALCON-HD study now aims to find out whether the drug is safe over time, which dose offers the best balance of benefits and risks, and, most importantly, whether people taking SKY-0515 experience meaningful clinical benefits compared with those receiving placeboplacebo A placebo is a dummy medicine containing no active ingredients. The placebo effect is a psychological effect that causes people to feel better even if they’re taking a pill that doesn’t work.. These answers will take time. Even positive trial results would need careful evaluation before regulators could consider approving the treatment.

For now, FALCON-HD represents another important step in a growing pipeline of potential HD treatments. We look forward to future updates on this program. 

Summary

• Skyhawk has begun dosing people in the US in the FALCON-HD study, a major international trial of its experimental once-daily pill, SKY-0515.
• SKY-0515 is lowers huntingtin and PMS1, targeting two biological processes implicated in HD.
• The FALCON-HD studies will test safety, dosing and effectiveness, including whether SKY-0515 can deliver meaningful slow signs and symptoms of HD.
• This is an encouraging milestone, but SKY-0515 has not yet been proven to slow HD progression.