Dosing Study of Ara-C/EL625/Idarubicin in Refractory and Relapsed AML

This clinical trial is designed to assess the ability of cenersen sodium (EL625) in combination with Idarubicin alone or with Cytarabine to either: (1) induce remissions in patients who have previously failed to go into remission in response to chemotherapy; or (2) provide patents who have relapsed after going into a chemotherapy-induced remission with a longer remission.

Cenersen sodium is one of a new class of drugs called antisense oligonucleotides (oligos). Oligos are designed to block the production of specific proteins and thereby inhibit their function. Cenersen sodium targets p53, a widely studied protein.

In cancer, p53 occurs either in the un-mutated ("normal") or mutated forms. The majority of participants in this trial are expected to have un-mutated p53. Cenersen sodium is anticipated to sensitize cancers with un-mutated p53 to most established cancer therapeutics.

p53 has a pivotal role in protecting the body from cells that have suffered genetic damage and, as a result, do not function properly. The protein first senses the level of the damage and then forces the damaged cell to respond to the damage either by repairing itself or committing suicide. In general, the greater the level of damage the more likely the cellular response will be suicide.

Many cancer therapeutics, including both chemotherapy and radiation, cause the types of genetic damage that activate p53 and, consequently, cause either damage repair or cellular suicide. Laboratory studies suggest that cancer cells have a host of defenses that reduce the chances that these cells will respond to genetic damage by committing suicide. So compared to normal cells, cancer cells are more likely to repair the damage caused by cancer therapeutics while normal cells are more likely to commit suicide. Thus, blocking un-mutated p53 is more likely to prevent repair in cancer cells while preventing suicide in normal cells. This provides the basis for a differential effect of cenersen sodium on cancer cells verses normal cells.

When p53-dependent repair is prevented in cancer cells they begin to copy their damaged genetic information in preparation for cell division. This copying of the genetic damage triggers a p53-independent backup suicide mechanism and, as a result, the cancer cells are eliminated. This is the presumed mechanism whereby cenersen sodium is able to sensitize cancer cells with normal p53 function to numerous cancer therapeutics.

At higher doses however, chemotherapy sometimes blocks cells from copying their genes in preparation for division. Thus, it is possible that a chemotherapeutic agent used at a high dose could block any sensitizing effect that cenersen sodium might otherwise have on the cancer.

The chemotherapeutic agent Idarubicin is known to produce the type of genetic damage that effects p53 expression, causes p53-dependent responses and has been shown to be made more effective at killing cancer cells by cenersen sodium. Cytarabine (Ara-C) is the most widely used chemotherapeutic agent for AML. Cenersen sodium does not appear to sensitize cancer cells to Cytarabine and at higher doses Cytarabine may reduce the capacity of cenersen sodium to sensitize cancer cells.

Hence, this AML study will examine the effects of Cenersen sodium used in combination with Idarubicin and one of three different doses of Cytarabine (i.e. 0, 0.1 and 1.0 gm/m2/day), on the responsiveness of participants to these chemotherapeutic agents.