Peter J. Thomford

Preclinical Safety Evaluation of rhuMAbVEGF, an Antiangiogenic Humanized Monoclonal Antibody

Recombinant humanized antivascular endothelial growth factor (rhuMAbVEGF) is a monoclonal IgG, antibody that is being developed as an antiangiogenic agent for use in treating a variety of solid tumors. Preclinical safety studies included an immunohistochemical tissue cross-reactivity study, in vitro hemolytic potential and blood compatibility studies, and multiple dose toxicity studies. Toxicity studies were conducted in cynomolgus monkey because rhuMAbVEGF is pharmacologically active in this species and does not bind rat or mouse vascular endothelial growth factor (VEGF). Following twice weekly administration of rhuMAbVEGF for 4 or 13 wk, young adult cynomolgus monkeys exhibited physeal dysplasia characterized by a dose-related increase in hypertrophied chondrocytes, subchondral bony plate formation, and inhibition of vascular invasion of the growth plate. In addition, decreased ovarian and uterine weights and an absence of corpora lutea were observed in females receiving 10 and 50 mg/kg/dose in the 13-wk study. Both the physeal and ovarian changes were reversible with cessation of treatment. No other treatment-related effects were observed following rhuMAbVEGF administration at doses up to 50 mg/kg. These findings indicate that VEGF is required for longitudinal bone growth and corpora lutea formation and that rhuMAbVEGF can reversibly inhibit physiologic neovascularization at these sites.

The Mechanisms of Action of Reproductive Toxicants

Successful human reproduction is a complex process which requires normal function of 2 individuals. Reproductive toxicants can impair reproduction by acting in the male, female or both. Reproductive toxicants can produce their adverse effects by several direct and indirect mechanisms. The mechanisms by which reproductive toxicants impair reproduction are reviewed.

Effect of oocyte number and rate of atresia on the age of menopause.

Menopause occurs when oocyte number falls below the threshold required for ovarian function. The age of menopause is decreased by some drugs, some occupational exposures, and cigarette smoke (both active and passive). Using data collected by Block (Acta Anat (Basel) 1954; 14:208), we have constructed four, two parameter models to explore the effect of oocyte number and rate of atresia on age at menopause. The models used are: linear [O(A) = OB + R * A]; natural log [O(A) = R * In (A)]; exponential [O(A) = OB * exp(R * A)], and power [O(A) = OB * Age(R)]. OB = oocyte number at birth, ATR = rate of atresia, and O(A) = number of oocytes at age A. The parameters for the four models are: (formula; see text) Each model has different behavior with respect to alterations in oocyte number and rate of atresia on age at menopause. Animal studies suggest that ovarian failure is only weakly dependent on oocyte number, consistent with the power and exponential models. These suggest that the decrease in age at menopause following xenobiotic exposures results from an increase in the rate of atresia.

Ovarian toxicity of benzo(a)pyrene and metabolites in mice

The effect of intraovarian injection of benzo(a)pyrene (BP) or one of three metabolites: +7,8-oxide (7,8-O), (-)-dihydrodiol (DHD), and (+)-diol-epoxide-2 (DE2) on ovarian volume, weight, and follicle number was investigated in DBA/2N (D2), C57BL/6N (B6), and (DBA/2N x C57BL/6N)F1 (F1) mice. Female mice, 6 to 8 weeks old, were treated by injection into the right ovary with the indicated compound (10 micrograms in 1 microL DMSO). The left ovary was untreated. Two weeks following treatment both ovaries were removed, fixed in Bouins medium, serially sectioned, and stained with hematoxylin and eosin. Right ovarian weight was decreased in D2 mice treated with BP (P less than 0.01 and DHD (P less than 0.01). Left ovarian weight was increased in D2 mice treated with DE2 (P less than 0.05). BP decreased right ovarian volume in D2 (P less than 0.01) and F1 (P less than 0.01) mice. 7,8-O decreased right ovarian volume in D2 mice (P less than 0.05). DHD decreased right ovarian volume in D2 (P less than 0.01) and F1 (P less than 0.05) mice. DE2 decreased right ovarian volume in D2 (P less than 0.01) and F1 (P less than 0.01) mice. Left ovarian volume was increased in B6 (P less than 0.01) and D2 (P less than 0.05) mice treated with DE2. The number of small follicles was decreased in D2, B6, and F1 mice treated with DE2 (P less than 0.01). BP and DHD also decreased small follicle number in D2 and F1 mice (P less than 0.01). The number of growing follicles was decreased in B6, D2, and F1 mice treated with DE2 (P less than 0.01). Treatment with DHD decreased the number of growing follicles in D2 mice (P less than 0.05). The number of antral follicles was reduced in F1 mice treated with BP (P less than 0.05), DHD (P less than 0.01), and DE2 (P less than 0.01). The number of antral follicles was also reduced in B6 mice treated with DE2 (P less than 0.01) and in D2 mice treated with DHD (P less than 0.05) and D2 mice treated with DE2 (P less than 0.01). These experiments suggest that toxic effects to one ovary may result in compensatory hypertrophy of the contralateral ovary. Morphometric analysis of the ovary, including ovarian volume, represents a useful objective measure of ovarian toxicity.

Transport and metabolism of dexamethasone in the dually perfused human placenta.

Dexamethasone (DEX), a synthetic glucocorticoid, has been suggested to accelerate fetal lung maturation and is sometimes used clinically during premature labor for this purpose. These experiments were initiated to measure the rate of transfer and metabolism of DEX by the human placenta. Lobules from full term (38-41 weeks) human placentas, obtained immediately after delivery, were perfused on both maternal and fetal sides. Radiolabeled (14C) DEX and tritiated water were infused into the maternal artery. Samples were taken at timed intervals throughout the perfusion period from the maternal artery (MA), maternal vein (MV), fetal artery (FA) and fetal vein (FV). Transport was determined by liquid scintillation spectroscopy and metabolism of DEX was determined by reversed phase HPLC. Tritiated water reached equilibrium between the maternal and fetal circulations within 75 min of perfusion, while total 14C-labeled radioactivity attained equilibrium after 180 min. HPLC revealed one metabolite of DEX which co-migrated with an 11-ketobetamethasone standard. The concentration of metabolite at 10, 30, 120, and 240 min in the FV were 9, 22, 40, and 41 ng/ml, respectively, and in the MV were 15, 28, 46, and 48 ng/ml, respectively. However, the ratio of metabolite/DEX was greater at 10 min in the FV (0.39) than in the MV (0.08). These data suggest that DEX crosses the human term placenta, that an enzyme in the placenta metabolizes DEX into an 11-keto-metabolite, and that a greater metabolite:DEX ratio is found at earlier times in the fetal circulation than in the maternal circulation.

Twenty-four-hour progesterone and luteinizing hormone profiles in the midluteal phase of the infertile patient: correlation with other indicators of luteal phase insufficiency

Abstract The authors have further analyzed women diagnosed as having luteal phase insufficiency in hope of determining the value of specific screening tests as well as determining the degree of heterogeneity of pathophysiologic mechanisms involved in the disorder. Twelve women with the disorder were identified, 6 with two consecutive midluteal serum progesterone (P) levels