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How do they work?

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How might microbicides work?

Researchers are exploring diverse and increasingly sophisticated mechanisms of action to block HIV infection. At this point, it is unknown whether the ways in which various microbicides work – their mechanisms of action – will actually prevent HIV infection. The efficacy of microbicides with different mechanisms of action may also vary significantly.

Microbicides with different mechanisms of action will affect the HIV lifecycle in different ways. Some microbicides even attack HIV at multiple points in its lifecycle.

Each mechanism of action presents potential benefits and challenges. In addition, each product in development has different characteristics according to whether or not it is:

  • Contraceptive
  • Protective against other STIs, along with HIV
  • Long or short acting

Current approaches to preventing HIV infection fall into two main categories: those that are Broad Spectrum (meaning that they work against a broad range of cells and pathogens) and those that are ARV Based.

Broad Spectrum Microbicides

ARV-Based Microbicides

  • Prevents the STI from entering healthy cells by creating a barrier between the virus and the healthy cells
  • Blocks specific proteins on the virus so that it cannot attach to a healthy cell
  • Boosts the vagina's natural defense system
  • Blocks specific receptors on the healthy cells so that the virus cannot attach itself
  • Destroys the virus by attacking it
  • Stops the virus from making copies of itself by deactivating a key component necessary to do this

 
  • Stops the virus from copying itself once it has started

Just as each mechanism of action intercepts or inhibits HIV infection at different points in the infection lifecycle, each 'mechanism of action' has different consequences for the likely characteristics of the product.

Microbicides are scientifically achievable.

At least five international scientific meetings have concluded that microbicide development is both necessary and feasible [See timeline]. The Rockefeller Foundation convened a high level panel of scientists to evaluate the field and identify opportunities for accelerating microbicide science. The Scientific Working Group of the Rockefeller Initiative concluded:

Accelerating the development of microbicides is a realistic and important near-term opportunity. The challenges facing microbicide development are well understood and manageable. The first generation of microbicide products is now undergoing clinical testing, and, if effective, should be on the market well within this decade. Subsequent product generations will deliver improved effectiveness, a broader spectrum of activity, and enhanced acceptability for consumers.

For the entire Rockefeller report on science, click pdf

The pipeline of potential products is full and promising.

  • More than 50 product leads are under development
  • 11 of these products are currently in clinical trials
  • Three products are in phase II/IIB trials and phase III effectiveness trials (the last stage of testing)
  • The rest are in human safety testing

More on products in the pipeline...