SILCAAT investigators say that IL-2 study should not stop

Keith Alcorn
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This article is more than 22 years old.

SILCAAT, the international clinical endpoint study of IL-2 terminated by Chiron this week, should not close, say the study’s Scientific Committee. They remain convinced that a clinical endpoint study in people with CD4 counts between 50 and 299 cells/mm3 is necessary, despite Chiron's decision to close the study and seek licensing for IL-2 on the basis of changes in CD4 cell count (see October 24 news item.

In a statement issued yesterday, the Scientific Committee said:

"Chiron has recently announced their closure of the SILCAAT study as part of a unilateral business decision. We understand the need for such difficult decisions on the part of a company. In this instance the decision seems particularly tragic to us insofar as it terminates a study that is fully enrolled and at the last DSMB meeting was noted to be proceeding as planned with intact assumptions regarding sample size.”

Glossary

endpoint

In a clinical trial, a clearly defined outcome which is used to evaluate whether a treatment is working or not. Trials usually have a single primary endpoint (e.g. having an undetectable viral load) as well as a few secondary endpoints, covering other aspects of treatment safety, tolerability and efficacy.

sample size

A study has adequate statistical power if it can reliably detect a clinically important difference (i.e. between two treatments) if a difference actually exists. If a study is under-powered, there are not enough people taking part and the study may not tell us whether one treatment is better than the other.

sample

Studies aim to give information that will be applicable to a large group of people (e.g. adults with diagnosed HIV in the UK). Because it is impractical to conduct a study with such a large group, only a sub-group (a sample) takes part in a study. This isn’t a problem as long as the characteristics of the sample are similar to those of the wider group (e.g. in terms of age, gender, CD4 count and years since diagnosis).

salvage therapy

Any treatment regimen used after a number of earlier regimens have failed. People with HIV who have experienced side-effects and/or developed resistance to many HIV drugs receive salvage therapy, sometimes consisting of a large number of medications.

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).

“Accordingly, upon being informed of this decision, we have initiated efforts to salvage this important phase III trial by engaging in discussions with Chiron on how the study might be transitioned to an academic based platform under the direction of the investigators.

At this time we do not know whether or not we will be successful in achieving this transition. However, we are asking your support in retaining patients on study until such time as these discussions have come to completion. We would very much appreciate your feedback on this issue and an indication as to whether or not you would be willing to continue to follow the patients currently enrolled on the study under the auspices of an investigator led study."

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