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Biomedical subjects

K Hellmann

Publications and source records attributed to K Hellmann.

At least 37 records · Page 2Linked to original sources
PubMed1991

Radiotherapeutic enhancement by razoxane.

Razoxane blocks cell division in the G2/M phase of the cell generation cycle and appears to normalize tumour neovasculature development. These were the principal reasons for the examination and probably for the demonstration of the radiosensitizing activity of Rz. Specially intriguing has been the finding that radiation of primary tumour implants in animals treated with Rz has a powerful potentiating effect on the antimetastatic activity of the combination. This concept has not yet received any clinical examination. Clinical trials with radiotherapy and Rz have demonstrated the clearest beneficial effects in terms of response rates and maintained local control in soft tissue sarcomas and possibly in recurrent rectal and in bladder carcinomas. Interesting heightened activity has also been found in hepatic metastases from gastrointestinal tumours. Carcinomas of the cervix, bronchus and head and neck, however, have not shown any benefit from the combination compared with radiotherapy alone.

Animals↗
PubMed1989

The pyrimido-pyrimidine derivatives RA233 and RX-RA85 affect cell cycle distribution of two murine tumour cell lines.

The pyrimido-pyrimidine derivatives RA233 and RX-RA85, which are potent inhibitors of platelet and tumour phosphodiesterases, were developed as antitumour agents. Clinical as well as animal studies suggest a tumour type specific, although moderate, antitumour activity for RA233. In our search for more potent congeners of RA233, we found that RX-RA85 was cytotoxic for cultured B16 melanoma and Lewis lung carcinoma cells at drug concentrations above 4 micrograms/ml whereas RA233 concentrations up to 400 micrograms/ml were tolerated. When tested for their effects on cell cycle distribution, RX-RA85 was 100-fold more potent than RA233 in producing an increase in the proportion of cells in S and G2 + M phase in 3LL cells. Progression of 3LL cells through the cell cycle was delayed for 5 h by RA233 treatment, whereas RX-RA85 was ineffective. In contrast, B16 cells responded poorly to either drug. The effects of both compounds were not only tumour cell specific but also dependent on the stage of tumour cell growth (drugs added to synchronously vs. asynchronously growing cultures). In the case of RX-RA85, the potency to affect tumour cell cycle distribution was highly dependent on tumour cell number, making the potential of this drug as an antitumour agent somewhat limited.

Animals↗
PubMed1989

ICRF 187.

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Animals↗
PubMed1987

Reduction of vincristine toxicity by Cronassial.

A mixture of gangliosides (Cronassial) protects against the chronic but not the acute lethal toxicity of vincristine in mice and affords some protection against the acute lethal toxicity of vincristine in chicks. The protective effect of Cronassial appears to be greatest near the LD50 of vincristine and then diminishes as the dose of vincristine increases further. Cronassial does not, however, reduce the vincristine antitumour activity, so that the net effect is an improvement in the vincristine therapeutic index. Clinical trials are underway to examine the effect of the combination on the development of neurotoxicity in cancer patients.

Animals↗
PubMed1986

Randomized trial of oral adjuvant razoxane (ICRF 159) in resectable colorectal cancer: five-year follow-up.

Razoxane is one of the few agents which has shown activity in the treatment of advanced colorectal cancer. The drug has therefore been evaluated in a prospective randomized controlled trial as an adjuvant to surgery for resectable colorectal cancer. The results to median follow-up of 5 years are reported here. Accrual has ceased and a total of 272 patients entered the trial (133 control, 139 treatment). Treated patients received razoxane postoperatively on a continuous, long-term basis while control patients received identical clinical care but no adjuvant chemotherapy. Analysis of the results shows a significant prolongation of the time to recurrence for Dukes' C patients. All other groups including the overall analysis show no benefit although there is a consistent trend in favour of the treated patients except in Dukes' group 'D'. Razoxane is tolerated well by patients and causes minimal side-effects. However acute leukaemia occurred in three patients (2.45 per cent) after prolonged exposure to the drug and further evaluation should be in patients who are at high risk of developing recurrent cancer, in whom such a risk may be acceptable. It is concluded that razoxane is suitable for further evaluation in colorectal cancer and for incorporation into combination chemotherapy regimens.

Clinical Trials as Topic↗
PubMed1985

Antiplatelet pyrimido-pyrimidines and metastasis.

The role of antiplatelet drugs in relation to their potential antimetastatic activities has been reviewed and the effects of two pyrimido-pyrimidine derivatives (RX-RA69 and RX-RA85) with strong antiplatelet activities investigated in metastasizing tumour models. The routes of administration and drug dosages were always chosen in such a way that good antiplatelet activities were obtained. RX-RA69 (20 mg/kg/day) given in the drinking water had no effect on spontaneous metastasis of Lewis lung carcinoma. RX-RA85 (20 mg/kg/day) did not influence spontaneous metastasis of B16 melanoma. On the other hand, giving RX-RA85 (8 mg/kg) daily i.p. to Lewis lung carcinoma bearing mice significantly increased the number of lung metastases but had no significant effect on primary tumour implant growth. Pretreating mice orally with 20 mg/kg RX-RA85 1 h before i.v. injection of B16 melanoma cells had no significant effect on lung colony number or distribution of extrapulmonary tumours while injecting the same dosage of RX-RA85 i.v. 1-2 h before tumour-cell injection decreased lung colony formation, but increased extrapulmonary tumour burden. This investigation like many others does not support the importance of platelets in metastasis formation.

Animals↗
PubMed1983

Effect of AT1727 on growth and metastasis of murine tumours.

AT1727 was tested on 5 different murine tumour systems. Compared with its analogue, razoxane, AT1727 was less effective at multiple low doses against sarcoma 180 and L1210 leukaemia. A single high-dose treatment with AT1727 was, however, more active than razoxane. AT1727 inhibited the growth of the Lewis lung primary tumour and significantly reduced the number of pulmonary metastases. Although AT1727 showed a slight inhibitory effect on the growth of the B16 primary, it had no effect on the metastases.

Animals↗
PubMed1982

Adjuvant oral razoxane (ICRF-159) in resectable colorectal cancer.

One hundred and seventy six patients (81 controls, 95 receiving treatment) have entered a prospective randomized trial of long-term oral adjuvant razoxane (ICRF-159) following removal of a colorectal cancer. The median follow-up is 34 months. The treated patients in Dukes' groups B and C have a significantly longer disease-free interval than the control patients (P = 0.01 'as randomized' and P = 0.004 'as treated'). The differences in survival for Dukes' groups B and C are not significant, although follow-up is short. In Dukes' groups B and C, however, 24 of 56 of the patients in the control group have died (43%), as against only 17 of 64 in the treatment group (27%). The treatment produces very few side-effects, is well tolerated by patients, and is taken orally.

Administration, Oral↗
PubMed1982

Razoxane penetration into the cerebrospinal fluid of rats.

Razoxane (100 mg/kg) was administered to rats as a single IP dose. Plasma and CSF samples were obtained at intervals varying from 15 min to 24 h after dosing, and the razoxane was assayed by a new and simple high performance liquid chromatography (HPLC) technique. Razoxane was absorbed quickly from the peritoneal cavity; it reached a peak concentration within 0.5 h and decayed with a half-life of 1.6 h. Only 10% of the plasma razoxane available entered the CSF, reaching a peak concentration by 2h, which was maintained for a further 4 h, and finally decaying to reach 10% of its peak value by 8 h.

Animals↗
PubMed1981

A controlled prospective trial of adjuvant razoxane in resectable colorectal cancer.

Following resection of their tumour, 162 patients with colorectal cancer entered a prospective randomized controlled clinical trial of adjuvant oral razoxane. Thirty-one patients were Duke's group A; 49 group B; 61 group C; and 17 group D; an additional four patients were randomized in error. The adjuvant group received the usual clinical care and 125 mg razoxane twice daily for 5 consecutive days (monday-friday) every week indefinitely. Control patients received the same clinical care as the adjuvant group, but no razoxane. At 3 years, 134 patients (84%) are evaluable. The recurrence rate in the first 6 months was 20% and 28% respectively in the Duke's B and C controls compared with 4% and 9% in the corresponding razoxane treated patients. Most recurrences occurred within the first 6 months from randomization. When all patients as randomized are included in the analysis of survival, irrespective of whether they were cured by surgery (Duke's A), had advanced cancer (Duke's D), or took no razoxane when randomized to take it, then as might be expected any differences there may be between the razoxane-treated and control patients with minimal residual disease (Duke's B and C) are so distorted that the p value of the difference in survival was 0.93. If however only patients with Duke's group B or C are taken (49 controls and 47 treated), log-rank analysis reveals a difference in the cancer mortality curves (p = 0.07). If patients who had been randomized to take razoxane, but who had not taken it at any time (and therefore received the same treatment as controls) are analysed with the controls, the difference between the two groups increases further, with p less than 0.05. The razoxane-treated patients experienced no significant toxicity apart from a readily reversible mild leukopenia in 52% while gastrointestinal symptoms necessitated stopping the drug in only four patients. These four all took the drug for less than 4 weeks. Because there was no toxicity to subtract from any benefit razoxane adjuvant treatment produced and the quality of life was not impaired, the therapeutic benefit of surgery wsa increased to the extent that razoxane increased survival of patients with Duke's B and C tumours.

Clinical Trials as Topic↗