PNU-159548, a novel cytotoxic antitumor agent with a low cardiotoxic potential

Cardiac troponin-T and CK-MB (mass) levels in cardiac and non cardiac disease

Serum cardiac troponin T (cTnT) and CKMB (mass) were analysed in three groups of patients. The first group (n=32) were patients with acute coronary syndromes including myocardial infarction. The second group (n=35)were patients with hypertension. The third group (n=24) were patients who had succumbed to non cardiac diseases. In all 3 groups, cardiac troponin T was elevated when compared with controls (p<0.001). However, CKMB elevation was not significant in all groups. CKMB levels correlated well with troponin T levels only when CKMB was greater than 50 ng/ml (r=1.00). Small elevations of troponin T identifies minimal cardiac necrosis and patients can benefit from early invasive therapy.

Aziridine alkaloids as potential therapeutic agents

The present review describes research on natural aziridine alkaloids isolated from both terrestrial and marine species, as well as their lipophilic semi-synthetic, and/or synthetic analogs. Over 130 biologically active aziridine-containing compounds demonstrate confirmed pharmacological activity including antitumor, antimicrobial, antibacterial effects. The structures, origin, and biological activities of aziridine alkaloids are reviewed. Consequently this review emphasizes the role of aziridine alkaloids as an important source of drug prototypes and leads for drug discovery.

Cardiac troponin is the most effective translational safety biomarker for myocardial injury in cardiotoxicity

There is an overwhelming weight of evidence that certifies cardiac troponin (cTn) as the preferred, defacto, translational, safety biomarker for myocardial injury in cardiotoxicity. As well as being the gold standard for cardiac injury in man, it has been widely used for clinical assessment and monitoring of cardiac toxicity in humans being treated for cancer. Furthermore, several dozen preclinical published studies have directly confirmed its effectiveness in laboratory animals for assessment of cardiotoxicity. It is gradually being reverse translated from human into animal use as a safety biomarker. Its use is especially merited whenever there is any safety signal indicating potential cardiotoxicity and its required inclusion as a routine biomarker in preclinical safety studies seems on the horizon. There are some considerations that are unique to use of cTn assays in animals. Lack of awareness of these has, historically, significantly inhibited the introduction of cTn as a safety biomarker in preclinical toxicology. Firstly, cross-species reactivity is usually but not always high. Secondly, there is a background of cardiac injury that needs to be controlled for, including spontaneous cardiomyopathy in Sprague Dawley rats, and inappropriate blood collection methods. Also, there are faster kinetics of clearance in rats than for humans. Also, coincident muscle injury is frequent with cardiotoxicity and requires a skeletal muscle biomarker. Because cTn assays were developed for detection of gross cardiac necrosis, such as occurs with myocardial infarct, the more sensitive assays should be used for preclinical studies. However, analytic sensitivity is higher for standard preclinical studies than for clinical diagnostic testing because of use of concurrent controls and use of batch analysis that eliminates interassay variability. No other biomarker of myocardial injury comes close to cTn in effectiveness, including CK-MB, LDH-1 and 2, myoglobin, and FABP3. In addition to the use of cTn for monitoring active myocardial degeneration, there is growing evidence that measurements of brain natriuretic peptide (BNP) may be effective for monitoring drug-induced left ventricular dysfunction.

Troponin as a marker of myocardiac damage in drug-induced cardiotoxicity

Cardiac troponins T and I (cTnT and cTnI) are becoming the serum biomarkers of choice for monitoring potential drug-induced myocardial injury in both clinical and preclinical studies. The utility of cardiac troponins has been mainly demonstrated following the administration of antineoplastic drugs and beta-sympathomimetics, although the routine use of these markers in the monitoring in patients who received anthracyclines therapy is far from settled. Unlike the previous markers, which suffered from numerous shortages, the main advantages of cardiac troponins are their high specificity and sensitivity, wide diagnostic window and the possibility to use commercially available assays in clinical settings as well as in a broad range of laboratory animals. Nevertheless, in spite of vigorous research in this area, a number of questions are still unanswered and these are discussed in this review. The main problems seem to be the lack of standardisation of variety of troponin immunoassays, the assessment of suitable cutoff for drug-induced cardiotoxicity and determination of critical diagnostic window related to the optimal timing of sample collection, which may be drug-dependent.

4-Demethoxy-3′-deamino-3′-aziridinyl-4′-methylsulphonyl-daunorubicin (PNU-159548): A promising new candidate for chemotherapeutic treatment of osteosarcoma patients

The effectiveness of the alkycycline 4-demethoxy-3'-deamino-3'-aziridinyl-4'-methylsulphonyl-daunorubicin (PNU-159548, ladirubicin), a new drug with high antitumour activity against a broad range of neoplasms, was evaluated by using a panel of 32 human osteosarcoma cell lines, including cell lines resistant to doxorubicin, methotrexate, or cisplatin. PNU-159548 resulted to be highly active in all cell lines. No cross-resistance was found with conventional drugs, being PNU-159548 active also in cells resistant to doxorubicin and with a multidrug resistance phenotype (associated with MDR1 gene/P-glycoprotein overexpression), as well as in cells resistant to methotrexate or to cisplatin. Analysis of drug-drug interactions showed that PNU-159548 could be successfully used in combination with all the most important drugs currently used in OS chemotherapy. In fact, the simultaneous administration of PNU-159548 and doxorubicin, methotrexate, or cisplatin produced mostly additive or synergistic effects. Sequential exposure to PNU-159548 followed immediately by doxorubicin, methotrexate, or cisplatin was the most effective sequence of administration, invariably resulting in additive or synergistic effects in both drug-sensitive and drug-resistant osteosarcoma cell lines. In conclusion, the high in vitro effectiveness, the absence of cross-resistance with doxorubicin, methotrexate, or cisplatin and the possibility to be successfully used in combination with these drugs indicate PNU-159548 as a promising candidate to be considered for planning new therapeutic regimens for osteosarcoma patients, who show a decreased response to conventional chemotherapy.

Anthracyclines: Molecular Advances and Pharmacologic Developments in Antitumor Activity and Cardiotoxicity

The clinical use of anthracyclines like doxorubicin and daunorubicin can be viewed as a sort of double-edged sword. On the one hand, anthracyclines play an undisputed key role in the treatment of many neoplastic diseases; on the other hand, chronic administration of anthracyclines induces cardiomyopathy and congestive heart failure usually refractory to common medications. Second-generation analogs like epirubicin or idarubicin exhibit improvements in their therapeutic index, but the risk of inducing cardiomyopathy is not abated. It is because of their janus behavior (activity in tumors vis-à-vis toxicity in cardiomyocytes) that anthracyclines continue to attract the interest of preclinical and clinical investigations despite their longer-than-40-year record of longevity. Here we review recent progresses that may serve as a framework for reappraising the activity and toxicity of anthracyclines on basic and clinical pharmacology grounds. We review 1) new aspects of anthracycline-induced DNA damage in cancer cells; 2) the role of iron and free radicals as causative factors of apoptosis or other forms of cardiac damage; 3) molecular mechanisms of cardiotoxic synergism between anthracyclines and other anticancer agents; 4) the pharmacologic rationale and clinical recommendations for using cardioprotectants while not interfering with tumor response; 5) the development of tumor-targeted anthracycline formulations; and 6) the designing of third-generation analogs and their assessment in preclinical or clinical settings. An overview of these issues confirms that anthracyclines remain "evergreen" drugs with broad clinical indications but have still an improvable therapeutic index.

Cardiac troponin T as an indicator of reduced left ventricular contractility in experimental anthracycline-induced cardiomyopathy

PURPOSE

Cardiac troponin T (cTnT) plasma concentration is considered a useful marker of anthracycline-induced cardiomyopathy. In this study we used daunorubicin-treated Chinchilla rabbits as a model to investigate the relationship between left ventricular contractility and cTnT plasma concentrations.

METHODS

Two groups of animals were used: a control group (n=8) received i.v. saline, and an experimental group (n=11) received daunorubicin (3 mg/kg, i.v.). The substances were administered once weekly for 10 weeks, and 5-7 days after the last administration, left ventricular cardiac contractility (dP/dtmax) was invasively measured as a contractility index and blood was sampled for cTnT concentration determination (Elecsys Troponin T STAT immunoassay).

RESULTS

Cardiac contractility was significantly lower in seven surviving daunorubicin-treated animals than in control animals (745.7+/-69.3 vs 1393.4+/-25.5 kPa/s; P<0.001), while cTnT plasma concentrations were significantly increased (medians 0.278 vs 0.000 ng/ml; P<0.001). When the dP/dtmax values of individual daunorubicin-treated animals were plotted against the corresponding cTnT plasma concentrations, a close negative linear correlation was found (R=-0.910; P<0.005; regression equation: dP/dtmax=-1861*cTnT+1234).

CONCLUSIONS

This study suggests that determination of cTnT plasma levels, which is simple and inexpensive, could be used in anthracycline-treated patients for left ventricular systolic function assessment and contractility estimation.