sr-4554 and Hypoxia

To perform a Phase I study of SR-4554, a fluorinated 2-nitroimidazole noninvasive probe of tumor hypoxia detected by (19)F magnetic resonance spectroscopy (MRS).. SR-4554 administration, on days 1 and 8, was followed by plasma sampling for pharmacokinetic studies and by three MRS studies performed over 24 h on days 8 and 9. Unlocalized MR spectra were acquired from tumor (10- or 16-cm dual resonant 1H/19F surface coil; 1.5 T Siemens Vision MR system; 2048 transients acquired over 34 min; 1.28-ms adiabatic pulse; repetition time, 1 s). Plasma drug concentrations were measured with a validated high-performance liquid chromatography method. Noncompartmental pharmacokinetic analysis was performed.. Eight patients underwent pharmacokinetic studies, receiving doses of SR-4554 of 400-1600 mg/m(2). Peak plasma concentrations increased linearly with the SR-4554 dose (r(2) = 0.80; P = 0.0002). The plasma elimination half-life was relatively short (mean +/- SD, 3.28 +/- 0.59 h), and plasma clearance was quite rapid (mean +/- SD, 12.8 +/- 3.3 liters/h). Urinary recovery was generally high. SR-4554 was well tolerated. A single patient experienced dose-limiting toxicity (nausea and vomiting) at 1600 mg/m(2). The maximum tolerated dose was 1400 mg/m(2). SR-4554 was detected spectroscopically in tumors immediately after infusion at doses of 400-1600 mg/m(2). At the highest dose (1600 mg/m(2)), SR-4554 was detectable in tumor at 8 h, but not at 27 h.. SR-4554 has plasma pharmacokinetic and toxicity profiles suitable for use as a hypoxia probe. It can be detected in tumors by unlocalized MRS. Additional clinical studies are warranted.

Topics: Adult; Aged; Biomarkers, Tumor; Chromatography, High Pressure Liquid; Female; Fluorine Radioisotopes; Half-Life; Humans; Hypoxia; Infusions, Intravenous; Magnetic Resonance Spectroscopy; Male; Maximum Tolerated Dose; Metabolic Clearance Rate; Middle Aged; Neoplasms; Nitroimidazoles

Studies of pharmacokinetics (which is what the body does to the drug) and pharmacodynamics (which is what the drug does to the body) are essential components of the modern process of cancer drug discovery and development. Defining the precise relationship between pharmacokinetics and pharmacodynamics is critical. It is especially important to establish a well understood pharmacological "audit trail" that links together all of the essential parameters of drug action, from the molecular target to the clinical effects. The pharmacological audit trail allows us to answer two absolutely crucial questions: (1) how much gets there; and (2) what does it do? During the pre-clinical drug discovery phase, it is essential that pharmacokinetic/pharmacodynamic (PK/PD) properties are optimized, so that the best candidate can be selected for clinical development. As part of contemporary mechanistic, hypothesis-testing clinical trials, construction of the pharmacological PK/PD audit trail facilitates rational decision-making. However, PK/PD endpoints frequently require invasive sampling of body fluids and tissues. Non-invasive molecular measurements, e.g. using MRI or spectroscopy, or positron emission tomography, are therefore very attractive. This review highlights the need for PK/PD endpoints in modern drug design and development, illustrates the value of PK/PD endpoints, and emphasises the importance of non-invasive molecular imaging in drug development. Examples cited include the use of PK/PD endpoints in the development of molecular therapeutic drugs such as the Hsp90 molecular chaperone inhibitor 17AAG, as well as the development of SR-4554 as a non-invasive probe for the detection of tumour hypoxia.

Topics: Antineoplastic Agents; Benzoquinones; Diagnostic Imaging; HSP90 Heat-Shock Proteins; Humans; Hypoxia; Lactams, Macrocyclic; Magnetic Resonance Imaging; Magnetic Resonance Spectroscopy; Neoplasms; Nitroimidazoles; Positron-Emission Tomography; Rifabutin; Technology, Pharmaceutical; Ultrasonography

To perform a Phase I study of SR-4554, a fluorinated 2-nitroimidazole noninvasive probe of tumor hypoxia detected by (19)F magnetic resonance spectroscopy (MRS).. SR-4554 administration, on days 1 and 8, was followed by plasma sampling for pharmacokinetic studies and by three MRS studies performed over 24 h on days 8 and 9. Unlocalized MR spectra were acquired from tumor (10- or 16-cm dual resonant 1H/19F surface coil; 1.5 T Siemens Vision MR system; 2048 transients acquired over 34 min; 1.28-ms adiabatic pulse; repetition time, 1 s). Plasma drug concentrations were measured with a validated high-performance liquid chromatography method. Noncompartmental pharmacokinetic analysis was performed.. Eight patients underwent pharmacokinetic studies, receiving doses of SR-4554 of 400-1600 mg/m(2). Peak plasma concentrations increased linearly with the SR-4554 dose (r(2) = 0.80; P = 0.0002). The plasma elimination half-life was relatively short (mean +/- SD, 3.28 +/- 0.59 h), and plasma clearance was quite rapid (mean +/- SD, 12.8 +/- 3.3 liters/h). Urinary recovery was generally high. SR-4554 was well tolerated. A single patient experienced dose-limiting toxicity (nausea and vomiting) at 1600 mg/m(2). The maximum tolerated dose was 1400 mg/m(2). SR-4554 was detected spectroscopically in tumors immediately after infusion at doses of 400-1600 mg/m(2). At the highest dose (1600 mg/m(2)), SR-4554 was detectable in tumor at 8 h, but not at 27 h.. SR-4554 has plasma pharmacokinetic and toxicity profiles suitable for use as a hypoxia probe. It can be detected in tumors by unlocalized MRS. Additional clinical studies are warranted.

Topics: Adult; Aged; Biomarkers, Tumor; Chromatography, High Pressure Liquid; Female; Fluorine Radioisotopes; Half-Life; Humans; Hypoxia; Infusions, Intravenous; Magnetic Resonance Spectroscopy; Male; Maximum Tolerated Dose; Metabolic Clearance Rate; Middle Aged; Neoplasms; Nitroimidazoles

Tumor hypoxia is associated with poor prognosis and a more malignant tumor phenotype. SR-4554, a fluorinated 2-nitroimidazole, is selectively bioreduced and bound in hypoxic cells. We present validation studies of SR-4554 as a noninvasive hypoxia marker detected by fluorine-19 magnetic resonance spectroscopy ((19)F MRS) in the P22 carcinosarcoma, a tumor with clinically relevant hypoxia levels.. Tumor-bearing female severe combined immunodeficient mice received SR-4554 at 180 mg/kg. Pharmacokinetic studies of parent SR-4554 in plasma and tumors were performed using high-performance liquid chromatography-UV. Total SR-4554 (parent SR-4554 and bioreduction products) was monitored in tumor by (19)F MRS using a 4.7 T spectrometer, with continuous acquisition for up to 5 h. A parameter of total SR-4554 retention, the 3-h (19)F retention index ((19)FRI) was determined. Tumor pO(2), assessed polarographically, was decreased (5 mg/kg hydralazine or 100 mg/kg combretastatin A-4 phosphate) or increased [1 l/min carbogen (5% CO(2), 95% O(2)) plus 500 mg/kg nicotinamide], and the corresponding (19)FRI was measured.. Comparative HPLC-UV- and MRS-derived assessments of parent and total SR-4554, respectively, indicated that concentrations of total SR-4554 consistently exceeded parent SR-4554, the differential increasing with time. This indicates formation and retention of SR-4554 bioreduction products in tumor, confirming the presence of hypoxia. The (19)FRI was higher in hydralazine- and combretastatin-treated animals compared with unmodulated animals (P = 0.004 and 0.15, respectively) and animals receiving carbogen and nicotinamide (P = 0.0001 and 0.005, respectively). Significant correlations were demonstrated between mean (19)FRI and polarographic pO(2) parameters (P < 0.002).. Retention of hypoxia-related SR-4554 bioreduction products can be detected in the clinically relevant P22 tumor by (19)F MRS, and the (19)FRI correlates with polarographically measured pO(2). These findings support the use of SR 4554 as a noninvasive hypoxia marker.

Topics: Animals; Biomarkers, Tumor; Chromatography, High Pressure Liquid; Drug Evaluation, Preclinical; Female; Fluorine Radioisotopes; Hypoxia; Magnetic Resonance Spectroscopy; Mice; Mice, SCID; Neoplasm Transplantation; Neoplasms, Experimental; Nitroimidazoles; Oxygen; Polarography; Rats; Tissue Distribution

The purpose of this study was to examine the effect of carbogen gas (95% O2-5% CO2) on uptake and metabolism of 5-fluorouracil (5FU) in murine RIF-1 tumors and their growth in vivo. In addition, we have explored the mechanisms by which carbogen can transiently affect the physiology of RIF-1 tumors. After i.p. injection of 1 mmol/kg 5FU into C3H mice, the uptake and metabolism of the drug by s.c. RIF-1 tumors was followed for 2 h noninvasively using 19F-magnetic resonance spectroscopy (MRS). In all animals, irrespective of tumor size, carbogen caused a significant increase in the half-life (t(1/2)) of the elimination of 5FU by the tumor and a significant increase in growth inhibition. In 2-3-g tumors (group II), carbogen also caused increased 5FU uptake and metabolism to the cytotoxic 5-fluoronucleotides, whereas in 0.8-1.5-g tumors (group I), only the t(1/2) was slightly increased. These results suggested that tumor size was an important factor in the effect of carbogen on tumor physiology. Measurements of RIF-1 tumor vascular and necrotic volume showed no significant differences between group I and group II tumors. However, 1H-MR images of RIF-1 tumors showed that carbogen caused a transient decrease in signal intensity, which correlated positively (P = 0.02) with tumor size, suggesting that larger tumors responded to carbogen by transiently increasing O2 uptake from the blood. 19F-MRS was used to measure RIF-1 tumor retention of the fluorinated nitroimidazole SR-4554. These studies also showed a positive correlation (P = 0.001) with tumor size, implying greater hypoxia in larger tumors. We propose that carbogen may transiently open nonfunctional blood vessels in the tumor, allowing increased leakage of 5FU from the plasma into the extracellular space. 5FU transport is known to be pH dependent. Intra- and extracellular tumor pH was measured using 31P- and 19F-MRS, which showed that carbogen caused a significant decrease in the extracellular pH of 0.1 unit in group II tumors and a consequent increase in the negative pH gradient across the tumor plasma membrane, which can cause increased 5FU uptake. The pH gradient was unaffected in group I tumors. We conclude that carbogen breathing can increase tumor uptake of 5FU by two independent mechanisms involving changes in tumor blood flow and pH, which consequently cause increased formation of 5-fluoronucleotides and cytotoxicity. The effect seems more pronounced in hypoxic tumors, implying that carbogen would b

Topics: Animals; Biological Transport; Carbon Dioxide; Fibrosarcoma; Fluorouracil; Hydrogen-Ion Concentration; Hypoxia; Mice; Mice, Inbred C3H; Nitroimidazoles; Nuclear Magnetic Resonance, Biomolecular; Oxygen; Sarcoma, Experimental