FDA puts potentially long-acting, preventive drug for HAE on fast track
BW-20805 designed to be given every 3-6 months to prevent swelling attacks
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The U.S. Food and Drug Administration (FDA) has granted fast-track status to BW-20805, Argo Biopharma‘s long-acting investigational therapy for hereditary angioedema (HAE), which is intended to be given every three to six months to prevent swelling attacks in people with HAE.
Most available HAE drugs must be taken daily or are given, at maximum, about once per month. In a company press release announcing the new FDA designation, Argo noted that BW-20805 has “the potential for effective prevention of HAE attacks with a significant and longer-lasting therapeutic effect.”
The FDA’s fast track designation aims to accelerate the development and review of drugs for serious conditions that address unmet medical needs. This status gives companies more frequent communication with the FDA and lets them submit parts of their approval application early, helping the review process move faster.
An ongoing Phase 2 clinical trial (NCT06846398) is evaluating BW-20805’s ability to prevent swelling attacks in adults with HAE. Underway at more than a dozen locations worldwide, it involves approximately two dozen people ages 18-70. The trial is expected to wrap up by the end of the year, followed by plans for a global Phase 3 study, per Argo.
“Receiving [fast track designation] from the FDA highlights the significant unmet medical need for patients living with HAE and underscores the potential of BW-20805 as a novel therapeutic option,” said Dongxu Shu, PhD, cofounder and CEO of Argo. “We look forward to advancing the clinical development of BW-20805 and bringing a potentially long-acting treatment option to patients as effectively as possible.”
A chronic disease, HAE is characterized by recurrent episodes of swelling in the deeper layers of the skin or in the mucus membranes. HAE is caused by inherited gene mutations that drive overproduction of the signaling molecule bradykinin, which leads to blood vessel dilation and fluid leakage into surrounding tissues.
Several approved therapies are designed to lower bradykinin levels to prevent swelling attacks. These treatments work by controlling bradykinin production or blocking the activity or production of kallikrein, an enzyme that generates bradykinin.
Available therapies must be administered daily or every few weeks
Either way, however, these therapies are administered either daily or once every two to four weeks.
“Current prophylactic treatments are limited by frequent dosing, highlighting the need for long-acting, preventive therapies,” the company stated in its release.
BW-20805 consists of a small interfering RNA (siRNA) conjugated to N-acetylgalactosamine, enabling targeted delivery to liver cells. Once inside, the siRNA molecule blocks the production of prekallikrein, the precursor of kallikrein. It’s expected to prevent swelling attacks by providing durable reductions in prekallikrein, with potential dosing intervals of three to six months.
The open-label Phase 2 study is evaluating the safety and effectiveness of BW-20805 in preventing swelling attacks in 25 adults with HAE type 1 or 2. Participants were assigned to receive 600 or 300 mg doses, given as subcutaneous, or under-the-skin, injections. The higher dose is given every six months, while the lower dose is given every three months.
In February, Argo presented early trial data at the American Academy of Allergy, Asthma & Immunology (AAAAI) 2026 annual meeting. At that time, 14 people had received the treatment, and 10 had been followed long enough to evaluate its effects beyond the first month.
Among those participants, most (80%) remained completely free of swelling attacks after starting treatment. Across the different dosing groups, attack rates dropped substantially — by 100% in the highest-dose group, and by 87% to 89% in the lower-dose groups. Two participants who have been followed for about 169 days, or about six months, remained attack-free.
Levels of prekallikrein in the blood dropped quickly after dosing, by about 97% in the 600 mg group and by more than 92% in the combined 300 mg groups, within about three months. In the two participants followed for the longest period, these reductions reached 97%-98% by Day 169.
In terms of safety, BW-20805 has been generally well tolerated. The most common side effects were mild, short-lived reactions at the injection site. No serious side effects related to the treatment have been reported, according to the company.
“We have generated a robust body of clinical evidence supporting BW-20805’s potential, including recent open-label study results presented at the AAAAI Annual Meeting,” Shu said. Data “demonstrated that BW-20805 provides remarkable [prekallikrein] reduction and meaningful time-normalized HAE attack rate reduction.”
