http://www.acor.org:/lrg/
http://www.acor.org:/lrg/GIST?STI571_JN.pdf 

The experimental drug STI-571, now known as Glivec, is undergoing clinical trials against some forms of Leiomyosarcoma.   

It appears to be effective against LMS tumors that have a certain protein/enzyme active in their metabolism.  Testing of the tumors for the protein CD117 [or c-kit]  is necessary.  If the tumors are c-kit positive, [CD117 positive]  then approximately 80% to 90% of those tumors will respond to treatment with STI-571 [Glivec], and start shrinking.

Glivec is a designer drug, a Signal Transduction Inhibitor,  not a general chemotherapy drug. This means that the side effect profile is much milder than for the usual chemotherapy agents.  

Because of the early but VERY impressive  response to STI-571, we urge ALL abdominal tumors to be tested for CD117 [c-kit].  Because the CD117 [ c-kit] is sometimes, though rarely, expressed in LMS tumors which are not gastrointestinal, it might be a good idea to test every other patient as well.

STI-571 (Glivec) has now been successfully used in clinical trials against chronic myelogenous leukemia (which expresses bcr-abl) and against GIST (which expresses c-kit). There is some semantic and diagnostic confusion about the definition of GIST and whether c-kit positive tumors outside of the gastrointestinal area are technically GIST.  

There are a few other cancers which may also demonstrate c-kit. The most likely one, for which Novartis is planning clinical trials, is small cell lung cancer. This is quite different than large cell lung cancer, the more common disease.

There is also a possibility that STI-571 may work against cancers which demonstrate platelet derived growth factor (PDGFr). The most likely one, for which Novartis is planning clinical trials, is prostate cancer.

STI571 is a "designer" drug which targets a discreet number of cancers.

Tests for c-kit, or for anything else, are sometimes wrong. When confronted with conflicting results from two major medical centers, one may want to consider a third. It is hard to say which one of the first two was correct.     

April 2001