Cisplatin limitations

There are some serious drawbacks to the use of cis-platin in anticancer therapy. Severe toxicity problems occur, such as failure of the kidneys and bone marrow (nephrotoxicity and hematoxicity), nausea, intractable vomiting (emesis), peripheral neuropathy, deafness (ototoxicity), and seizures. These toxic side effects of cisplatin limit the dose that can be administered to patients typical doses are 100 mg day for up to five consecutive days. The nephrotoxicity can be reduced by hydration and diuresis. 5-HT3-receptor blockers control nausea and emesis. Much effort has been devoted to the development of chemopro-tective agents, which alleviate the side effects on normal tissues without compromising antitumor activity - mainly sulfur-containing agents such as sodium dithiocarbamate (Naddtc), 2-mercaptoethanesulphonate (mesna), and amifos-tine (WR-2721). Amifostine has recently been approved for coadministration with cisplatin, which reduces nephro- and neurotoxicity. ... 

Despite the imquestionable success story of cisplatin, limitations remain, including the powerfid toxic side effects. These toxic side effects include gastrointestinal problems such as acute nausea, vomiting, and diarrhea occasional liver dysfunction myelosuppression involving anemia, leukopenia, and thrombocytopenia ... 

ABT-888 (22) shows limited activity as monotherapy however, it strongly potentiates the activity of multiple DNA-damaging agents in preclinical models [39]. ABT-888 potentiated TMZ in a glioma model in a dose-dependent manner, with maximal efficacy achieved at 50 mg/ kg, which reduced tumor volume by 63%, 44% better than TMZ alone. In the MX-1 breast xenograft model, ABT-888, at 5 mg/ kg/ day in combination with cisplatin, caused sustained regressions in 8/9 mice compared to 3/9 for cisplatin monotherapy. 

In phase I clinical trials 47 patients, all of whom had previously failed standard treatments for solid tumors, received the drug in the UK, Italy, and Switzerland on three different schedules.123,124 Dose-limiting toxicities have been defined as bone marrow depression and diarrhea. The latter is treatable with loperamide. Signs of biological activity were seen. Notably one patient with metastatic pancreatic cancer showed a partial response (for 4 months) and two further patients, one with metastatic melanoma and one with bronchoalveolar carcinoma, also showed partial responses. In a phase I trial in combination with 5-FU, a partial response in breast cancer was observed.125 Furthermore, a reduction in tumor marker levels was observed in two patients, one with ovarian cancer, and one with colon cancer. Phase II studies have shown partial responses in cisplatin-resistant ovarian and nonsmall-cell lung cancer.126,127 The indications are that the profile of clinical activity is different and complementary to the mononuclear platinum agents. 

Pt(TV) Prodrugs. Platinum(IV) complexes have been widely studied as potential prodrugs that avoid the limitations of the cisplatin class of anticancer drugs. Indeed, the Pt(IV) compound satraplatin [Pt(cha)Cl2(OAc)2(NH3)] (cha, cyclohexylamine) is currently in clinical trials for treatment of hormone-refractory prostate cancer (Fig. 1) (22). Satraplatin is the first orally bioavailable platinum derivative under active clinical investigation and is particularly attractive because of the convenience of administration, milder toxicity profile, and lack of cross-resistance with cisplatin. These results are promising and support the idea that platinum(IV) complexes offer the opportunity to overcome some of the problems associated with cisplatin and its analogs. 

The conversion of the monofunctional adducts into bifunctional lesions depends drastically on the structure of the Pt drug. Obviously, Pt compounds exhibiting trans geometry form different bisadducts than cisplatin and hence, a different spectrum of antitumor activity is expected. Mechanistically, the formation and possible isomerization of bisadducts are not well understood. The assumption that hydrolysis of the second leaving group controls the formation of bisadduct may be an oversimplification. Studies with model compounds as well as with oligonucleotides have indicated that a certain nucleobase may be a powerful nucleophile toward Pt(II) if spatially in a correct position. Unfortunately, our knowledge on these interactions is at present very limited. 

The most frequently used regimen is cisplatin or carboplatin combined with etoposide. Irinotecan in combination with cisplatin has also been shown to be active (see Table 63-1). Overall response rates and survival durations are generally superior for patients with limited stage versus those with extensive stage disease. 

Domperidone [133], one of the most potent D2-dopamine blockers and antagonists of apomorphine-induced emesis with limited brain-blood barrier permeability, did not establish a position as an antiemetic, especially against cisplatin [134], Recently, the use of domperidone as a parenteral antiemetic has been discontinued because of serious cardiovascular toxicity. 

THC is effective in several chemotherapy regimens, including methotrexate and the doxorubicin/cyclophosphamide/fluorouracil combination. Cisplatin treatment, however, is more resistant. Side effects of THC are generally well tolerated, and use may be limited in the elderly or with higher doses. Nabilone is a synthetic cannabinoid that is more effective than prochlorperazine in chemotherapy-induced emesis, including cisplatin. Its side effects are similar to THC. Levonantradol is another synthetic cannabinoid with antiemetic effects, and may be administered orally or intramuscularly. The side effect of dysphoria may limit its use. 

Platinum is a relatively rare earth metal usually found with related metals osmium and iridium. While it has a number of industrial applications, its common consumer application is in catalytic converters. This application has actually increased platinum concentrations in roadside dust. The ability of platinum and its derivatives to kill cells or inhibit cell division was discovered in 1965. Platinum-based drugs, such as cisplatin, are used to treat ovarian and testicular cancer, and cancers of the head and neck, as well as others. Unfortunately, the toxic side effects of these agents often limit their usefulness. 

Turrisi AT 3rd, Kim K, Blum R, et al. Twice-daily compared with once-daily thoracic radiotherapy in limited small-cell lung cancer treated concurrently with cisplatin and etoposide. N Engl J Med 1999 340(4) 265-271. 

Levitan N, Dowlati A, Shina D, et al. Multi-institutional phase ITU trial of paclitaxel, cisplatin, and etoposide with concurrent radiation for limited-stage small-cell lung carcinoma. J Clin Oncol 2000 18(5) 1102-1109. 

Bremnes RM, Sundstrom S, Aasebo U, Vilsvik J. Paclitaxel in combination with cisplatin, etoposide and thoracic radiotherapy for limited stage small cell lung cancer (SCLC) a phase II study (abstract 1826). ProAmSoc Clin Oncol 1998 17 475a. 

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