IL-2 study in HIV patients halted; Chiron signals licensing bid soon [Correction]

Keith Alcorn
Estimated reading time 3 minutes
This article is more than 22 years old.

Chiron has announced that it is terminating the SILCAAT study of interleukin-2 treatment because the study design no longer meets the company's needs for licensing of the drug and is costing the company too much money.

The company hopes to submit licensing applications for IL-2 in the USA and European Union soon based on a analysis of existing data from the study, and to win marketing approval based on the effect of IL-2 on CD4 cell counts and viral load in patients who had a poor immunologic response to HAART. However, these data are not unblinded yet, and the company said there are no guarantees. Whilst previously reported studies suggest a benefit from IL-2 in this patient group, if SILCAAT data do not support licensing, a question mark will hang over the future use of IL-2 in HIV treatment.

"Continued improvements in HIV treatment (i.e., HAART) have led to reduced incidence of clinical events and a decrease in the overall rate of disease progression. Since the primary endpoint for the SILCAAT trial is time to first AIDS-defining event or death, decreases in clinical events and disease progression make the duration of time required to maintain a study of this magnitude infeasible for Chiron," said Craig Wheeler, President of Chiron, in a press release issued yesterday.

Glossary

hepatitis B virus (HBV)

The hepatitis B virus can be spread through sexual contact, sharing of contaminated needles and syringes, needlestick injuries and during childbirth. Hepatitis B infection may be either short-lived and rapidly cleared in less than six months by the immune system (acute infection) or lifelong (chronic). The infection can lead to serious illnesses such as cirrhosis and liver cancer. A vaccine is available to prevent the infection.

disease progression

The worsening of a disease.

phase II

The second stage in the clinical evaluation of a new drug or intervention, in which preliminary data on effectiveness and additional information about safety is collected among a few hundred people with the disease or condition.

immunotherapy

Use of immunologic agents such as antibodies, growth factors, and vaccines to modify (activate, enhance, or suppress) the immune system in order to treat disease. It is applied in the cancer field and in HIV research (attempts to eliminate the virus). Immunotherapy is also used to diminish adverse effects caused by some cancer treatments or to prevent rejection of a transplanted organ or tissue.

data safety monitoring board (DSMB)

An independent committee of clinical research experts that reviews data not available to the study team while a clinical trial is in progress to ensure that participants are not exposed to undue risks. A DSMB can recommend that the study be stopped if the intervention is not effective, is causing harm to participants or the study is not likely to serve its scientific purpose. Also known as an Independent Data Monitoring Committee (IDMC).

SILCAAT is an international randomised study of the use of IL-2 in people with CD4 counts between 50 and 300 cells/mm3 and undetectable viral load on a stable HAART regimen. The study was intended to follow patients for around four years in order to assess the effect of IL-2 treatment on the risk of opportunistic infections and death. Chiron has decided to terminate a study that is already estimated to have cost the company $20 million. Chiron has also terminated a study of a new hepatitis B treatment because it cannot find a development partner; HBV-MF59 is an immunotherapy for chronic HBV infection currently in Phase II trials

Patients already receiving IL-2 in SILCAAT will continue to receive IL-2 treatment if they want it, and data will continue to be collected on these individuals. The US National Institutes of Health-sponsored ESPRIT study of IL-2 treatment in people with CD4 cell counts above 300 will continue, and is still recruiting patients in the United Kingdom.

CORRECTION: the previous version of this story reported that Chiron needed to recruit 3,000 patients to the study. In fact, the recruitment target was 2,000, and 1957 participants had already joined the study by the time it was halted. We also reported that fewer clinical events had occurred than expected. We have been informed by Clifford Lane, a member of the Scientific Committee of the SILCAAT study, that this is not true, and that at the last DSMB review, the events rate was noted to be on target. Click here to read a statement from the study's Scientific Committee on why SILCAAT should not close.

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