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HIV, Tuberculosis, Hepatitis B, and Hepatitis C: Drugs, Diagnostics, Vaccines, and Microbicides in Development

by Lei Chou, Mark Harrington, Bob Huff, Richard Jefferys, Tracy Swan, Javid Syed, and Claire Wingfield

This Report was released at the XVII International AIDS Conference in Mexico City in August.

From the Introduction:

Treatment Action Group’s annual pipeline report is a review of medical technologies that stand a good chance of benefiting people with HIV within the next few years. It also covers those that may take longer to develop but represent innovation within the field.

This year our report has expanded to cover treatment and preventive vaccines for the hepatitis B virus and diagnostics for tuberculosis. These are natural extensions to our updates on HIV antiretroviral treatment, hepatitis C treatment, drugs and vaccines to treat and prevent tuberculosis, immune-based therapies for HIV, and HIV prevention technologies, including vaccines and microbicides.

In some areas, such as treatment for hepatitis C virus (HCV), the therapy pipeline is bubbling, with over 20 drugs listed in middle to late stages of development. Despite all the activity, no single drug is likely to revolutionize the current, difficult HCV treatment paradigm, though shortened treatment durations and increased rates of successful outcomes may begin to benefit people with HCV within the next few years. Unfortunately, people with HIV are often unnecessarily excluded from HCV research.

Tuberculosis (TB) is treatable and curable, yet it remains the top killer of people with HIV worldwide. A major limitation to broader and more effective TB treatment in the developing world is the lack of a simple and reliable means of diagnosis—and TB is especially hard to diagnose and treat in people with HIV. Hampered by limited investment in the field, the TB diagnostic pipeline mainly contains advances aimed at high-tech national laboratories or adaptations of existing technology that can be used in regional hospitals. There is much less on the horizon for TB diagnostics that can be used in rural settings, where the need is greatest.

TB drug therapy is also undergoing a period of renewed activity after decades of stasis. Five novel TB drugs are in clinical trials, and funding to explore improved treatment strategies with existing drugs has increased, though it lags far behind the need—especially in light of the growing problem of drug-resistant TB. As with HCV, the near-term goals for TB therapy are to reduce treatment times and improve success rates. Better TB treatment options for people with HIV are also a high priority.

Improved TB preventive vaccines offer the promise of cost-effective, wide-scale reductions in future cases of TB, though their impact may be decades away. A few candidates are in human trials, but many questions remain. One obstacle to getting the answers is the uncertainty of future funding for large-scale clinical trials of TB vaccines.

After a flurry of new drug approvals in the past year, the HIV treatment pipeline is slowing. Most gains in antiretroviral therapy over the next several years will likely come from treatment strategy refinements that build on recently approved drugs. Agents in the pipeline are generally expected to offer incremental, yet important, improvements over existing products. With interest in HIV drug research maturing, the field is ready for investment in a conceptual leap to discover radically new therapies that disable or even cure HIV infection, perhaps by unleashing innate mechanisms of anti-HIV immunity that the virus currently evades.

Interest in developing new treatments to control or eradicate hepatitis B virus (HBV) is slowly increasing, but the field is restricted by gaps in the scientific understanding of the virus. Current treatments—mostly spin-offs from HIV drug research—suppress HBV but, as with HIV, are vulnerable to the emergence of drug resistance. Exploration of strategies to prevent resistance, possibly through combination therapy, is the next frontier for HBV, with novel drugs much farther down the road.

The failure of two leading experimental agents in HIV prevention technologies has created a gloomy outlook for this field, though research is generally well funded and continues apace. An unexpected increase in HIV infections associated with a leading HIV vaccine candidate has stimulated a wrenching reappraisal of research priorities. With much greater understanding of the basic science of HIV needed, it may be said that the HIV vaccine field remains in a toddler state. Yet because no other intervention promises so much for future control of the epidemic, support for HIV vaccine research remains strong. The vaginal microbicide field also saw a leading candidate fail in a late-stage clinical trial. Other, likely stronger, microbicide candidates, are at earlier stages of development.

Research on therapies or vaccines to strengthen or stimulate the adaptive immune system to fight HIV remains the poor stepchild to drug and preventive vaccine science. Immune-based therapy research is closely associated with the scientific investigation of how HIV causes disease, and increased investment in this field may pay off in ways that are not immediately foreseeable. Agents in this pipeline tend to be earlier in development but represent a great variety of experimental and innovative approaches.

Research on new technologies to prevent, treat, and diagnose HIV and its coinfections is progressing in 2008. Some fields, such as HCV, are full of activity as drug sponsors race to be first in the market with a transformative therapy. Hepatitis B research may be the next field to get the attention of the commercial sector. Other fields, such as TB research, appear active because they are catching up after years of neglect, though the gap in the needed investment remains large. Antiretroviral research has made dramatic progress over the past 13 years, but seems to be entering a slow phase as recent advances are consolidated into the standard of care. For over 20 years, a preventive HIV vaccine has seemed perpetually just out of reach, though setbacks like the field has just experienced can create opportunities for new ideas to emerge.

Overall, the 2008 HIV pipeline suggests progress and hope. TAG’s 2008 Pipeline Report reveals not only the current status of these technologies but also underscores the need for continued and greater investment in making them useful and widely available.

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