Estimation of the hypoxic cell-sensitiser misonidazole and its O-demethylated metabolite in biological materials by reversed-phase high-performance liquid chromatography

Summary Experiments have been carried out both in vitro and in vivo to examine the possibility of chemosensitization by misonidazole (MISO) at concentrations which are achievable in the clinic. Using multicellular tumour spheroids in vitro we found that a 16h pre-incubation with 100pgml-1 MISO under hypoxic conditions led to a considerable enhancement of sensitivity to melphalan (MEL) but not to CCNU. Pre-incubation for 16h under hypoxia alone also produced a degree of sensitization to MEL, but there was no effect of oxic pre-incubation with MISO. In vivo experiments using the KHT or RIF-l tumours in C3H mice were designed so that repeated administration of MISO maintained blood concentrations of around 100 gml-l for either 7h or 16h. For the 7h regime, cytotoxic drugs were administered at the 4h point. In most experiments the tumour response to MEL, cyclosphosphamide (CTX), chlorambucil or CCNU was no greater in mice receiving multiple MISO than in mice receiving multiple injections of a balanced salt solution. In the occasional experiment where there was an apparent increase in response, the effect was only small (dose modifying factor <1.5). For the 16 h regime the effect was studied of administering CTX (100mg kg -') at various times during the regime. There was a clear trend towards increased CTX response in mice receiving multiple MISO compared with controls. There was, however, no clear tendency for the effect to increase with length of MISO pre-exposure.

Section: Discussioncontrasting

confidence: 55%

Section: Mice and Tumoursmentioning

confidence: 99%

An investigation of the possibility of chemosensitization by clinically achievable concentrations of misonidazole

Twentyman¹,

Workman²

1983

“…White-cell counts Blood samples were taken from non-anaesthetised (Workman et al, 1978) except that the mobile phase was 60% methanol/water.…”

Section: Mice and Tumoursmentioning

confidence: 99%

Chemosensitization by lipophilic nitroimidazoles

Twentyman¹,

Workman²

1983

“…Although benznidazole is used quite widely in South America to treat patients with the trypanosomal infection Chagas' disease or with mucotaneous Leishmaniasis Cerisola et al, 1978;Coura et al, 1978;Fava et al, 1978), apart from our preliminary studies (White et al, 1982) the only published data on its pharmacokinetics are for human plasma concentrations measured by polarography (Raaflub & Ziegler, 1979;Raaflub, 1980 (Brown & Workman, 1980;White et al, 1979Workman, 1980a (Workman & Brown, 1981) or the Amicon Micropartition system (Amicon, Woking) . Concentrations of benznidazole in plasma, ultrafiltrate, urine and tissue homogenates (25%-33% w/v) were determined by reversed-phase HPLC using an adaptation of the method described previously for misonidazole (Workman et al, 1978). Briefly, samples were treated with 2 vol methanol containing the internal standard 1-(2-nitroimidazol-1-yl)-3-ethoxypropan-2-ol (RoO7-0913, Roche) Pharmacokinetic parameters These were calculated as described in detail elsewhere Workman & Brown, 1981 For the experiment shown in Figure 3 the peak whole plasma concentrations (+2 s.e.)…”

mentioning

confidence: 99%

Preclinical pharmacokinetics of benznidazole

Workman¹,

White²,

Walton³

et al. 1984

Extensive studies have demonstrated that the response of mouse tumours to cytotoxic drugs can be enhanced by misonidazole (MISO) (1-(2-nitroimidazol-1-yl)-3-methoxypropan-2-ol, Ro 07-0582; Roche) (for reviews see McNally, 1982;Siemann, 1982). This enhancement, or chemosensitization, is usually greater than that seen in dose-limiting normal tissues, resulting in an improved therapeutic index. Because of the relatively high doses of MISO usually required for chemosensitization in mice (see above refs), and also because of its neurotoxicity in man (Dische et al., 1977), we have been interested in finding an improved chemosensitizer.In a detailed study of the structure-activity relationships for MISO analogues in combination with the nitrosourea CCNU (1-(2-chloroethyl)-3-cyclohexyl-l-nitrosourea) against the KHT tumour (Workman & Twentyman, 1982) we found that sensitizer lipophilicity was particularly important for chemosensitization. The lipophilic analogue benznidazole (N-benzyl-(2-nitroimidazolyl) acetamide, Ro 07-1051; Radanil; Roche), the structure of which is shown in Figure