Single Injection with Over Six-Month Efficacy: A Novel Long-Acting Candidate for HIV Therapy

Today, a latest paper published online in the top academic journal Nature introduced a novel small-molecule drug developed by the biopharmaceutical company Gilead Sciences, demonstrating the potential for long-acting treatment of HIV infection. Preliminary clinical studies showed that after a single injection of this drug in people living with HIV, their viral load decreased, and the drug remained active in the body more than six months post-injection.

The study authors pointed out in their paper that daily oral antiviral "cocktail" therapy provides a life-saving treatment for millions of HIV-infected individuals. However, some people develop resistance to multiple drugs, which weakens the effectiveness of the treatment. If patients cannot adhere to daily medication due to certain reasons, not only may the virus in their bodies resurge, but the risk of drug resistance will also increase, which is detrimental to treatment.

For this reason, researchers are dedicated to developing new long-acting medications, providing more treatment options for patients with HIV drug-resistant strains in their bodies, significantly reducing dosing frequency, and helping patients adhere to their treatment regimens.

Before introducing the drug discussed in this paper, let us briefly introduce the HIV virus. Within the viral particle, there is a unique cone-shaped protein shell known as the HIV capsid. The viral genome, along with reverse transcriptase and integrase, is enclosed within this shell. The capsid, formed by the self-assembly of capsid proteins, not only protects the viral genetic material but also facilitates the optimal interaction between the viral genes and enzymes at various stages of HIV infection, thereby enabling continuous viral production.

The authors of this study noted that most small-molecule antiviral drugs for treating HIV work by interfering with the virus’s reverse transcriptase or integrase, whereas the new drug, designated GS-6207, uniquely targets the capsid. Designed to bind tightly to HIV capsid protein, this small molecule disrupts capsid assembly and impairs its function.

In cell-based assays, scientists discovered that this small molecule exhibits broad-spectrum activity against more than 20 tested HIV strains, effectively inhibiting viral replication. It demonstrated an EC50 of 105 pM in MT-4 cells infected with HIV-1, showing greater potency than other approved antiretroviral drugs. Furthermore, GS-6207 produces synergistic effects when used in combination with other antiretroviral agents, leading researchers to consider it an ideal addition to “cocktail therapy.”

▲Molecular structure of GS-6207 (Image source: Reference [1])

Subsequently, researchers conducted preliminary clinical trials. In a randomized, double-blind, placebo-controlled, single-dose study involving 40 healthy individuals, subcutaneous administration of the drug was shown to be generally safe and well-tolerated. Moreover, GS-6207 exhibited slow and sustained drug release, with therapeutic activity maintained in the body for more than six months after a single injection.

Subsequently, researchers conducted a Phase I clinical trial in 32 patients with untreated HIV-1 infection. The results showed that viral load decreased in patients 9 days after a single dose, although it was not completely cleared.

▲In both healthy individuals and those infected with HIV-1, the activity of this small-molecule drug can be maintained for 24 weeks, reducing the viral load in infected individuals (Image source: Reference [1])

In conclusion, the researchers summarized that GS-6207, as a first-in-class HIV-1 capsid inhibitor, demonstrated favorable safety, prolonged pharmacokinetic exposure, and observed antiviral efficacy in humans, supporting its continued clinical development for the long-acting treatment of HIV infection. The study authors further noted that, due to the lack of need for frequent dosing, this small-molecule drug has the potential to become a candidate for preventing HIV infection in at-risk populations, although this requires validation in subsequent studies.

We look forward to positive outcomes from subsequent clinical studies of this innovative therapy, ultimately benefiting more individuals living with HIV-1.

References

[1] Clinical targeting of HIV capsid protein with a long-acting small molecule. Nature DOI: 10.1038/s41586-020-2443-1