Satraplatin

Satraplatin is an orally bioavailable platinum chemotherapeutic agent under development for several cancer types, including hormone-refractory prostate cancer (HRPC). Satraplatin is being developed for the treatment of men with chemorefractory HRPC for several reasons. Its relative ease of administration, potential lack of cross-resistance with other platinum agents, clinical benefits seen in early studies of HRPC, and an unmet need in this patient population after Docetaxel failure. Satraplatin may provide a palliative benefit for patients in terms of progression-free survival according to the most recent analyses of the phase III SPARC trial, and is currently under U.S. Food and Drug Administration (FDA) review for this indication. Whether satraplatin and prednisone offer an advantage over docetaxel retreatment or other cytotoxic agents in this setting is under investigation.[3]

Satraplatin has a favorable toxicity profile, and appears to have clinical activity against a variety of malignancies such as Breast Cancer, Prostate cancer and Lung cancer. The oral route of administration and the intermittent schedule makes it very convenient for clinical use. An indication has not yet been approved by the FDA. The only Phase III trial with satraplatin was conducted in pre-treated metastatic prostate cancer(CRPC), revealing an improvement in progression-free survival but no overall survival benefit.[5]

Many human tumors including testicular, bladder, lung, head, neck, and cervical cancers have been treated with platinum compounds.[5] All of the marketed platinum analogues must be administered via intravenous infusion is one of the main disadvantages for these platinum compounds due to severe, dose-limiting effects. An acquired resistance to cisplatin/carboplatin in ovarian cancer was discovered due to insufficient amounts of platinum reaching the target DNA or failure to achieve cell death. These drawbacks led to the development of the next generation of platinum analogues such as satraplatin[5]

Satraplatin is a prodrug, meaning it is metabolized in the body and transformed into its working form. The two polar acetate groups on satraplatin increase the drugs bioavailability, which in turn allows for a large fraction of the administered dose to make it into the bloodstream where metabolism begins. Once the molecule makes it to the bloodstream the drug loses its acetate groups. At this point the drug is structurally similar to cisplatin with the exception of one cyclohexylamine group in place of an amine group. Since the drug is now structurally similar to cisplatin its mechanism of action is also very similar. The chlorine atoms are displaced and the platinum atom in the drug binds to guanine residues in DNA. This unfortunately happens to not only cancer cells but other regular functioning cells as well causing some of the harsh side effects. By binding to guanine residues satraplatin inhibits DNA replication and transcription which leads to subsequent apoptosis. Where satraplatin differs is its cyclohexamine group. In cisplatin the two amine groups are symmetrical while satraplatin's cyclohexamine makes it asymmetrical which contributes to some of the drug's special properties.[3]

A large problem with cisplatin and other platinum based anti-cancer drugs is that the body can develop resistance to them. A major way that this happens is through a mammalian nucleotide excision repair pathway which repairs damaged DNA. However, some studies show that satraplatin compared to other platinum anti-cancer drugs can be elusive and are not recognized by the DNA repair proteins due to the different adducts on the molecule (cyclohexamine). Since satraplatin is not recognized by the DNA repair proteins the DNA remains damaged, the DNA cannot be replicated, the cell dies, and the problem of resistance is solved.[3]