Novel Bacterial Topoisomerase Inhibitor Gepotidacin Demonstrates Absence of Fluoroquinolone-Like Arthropathy in Juvenile Rats.

Fluoroquinolone use in children is limited due to its potential toxicity and negative effects on skeletal development, but the actual effects/risks of fluoroquinolones on bone growth and the mechanisms behind fluoroquinolone-driven arthropathy remain unknown. Gepotidacin is a novel, bactericidal, first-in-class triazaacenaphthylene antibiotic with a unique mechanism of action that is not anticipated to have the same risks to bone growth as those of fluoroquinolones. Gepotidacin is in phase III clinical development for uncomplicated urinary tract infections (ClinicalTrials.gov identifiers NCT04020341 and NCT04187144) and urogenital gonorrhea (ClinicalTrials.gov identifier NCT04010539) in adults and adolescents ≥12 years of age. To inform arthropathy and other potential toxicity risks of gepotidacin in pediatric studies, this nonclinical study assessed oral gepotidacin toxicity in juvenile rats from postnatal day (PND) 4 to PND 32/35 (approximately equivalent to human ages from newborn to 11 years), using both in-life assessments (tolerability, toxicity, and toxicokinetics) and terminal assessments (necropsy with macroscopic and microscopic skeletal femoral head and/or stifle joint examinations). Gepotidacin doses of ≤300 mg/kg of body weight/day were well tolerated from PND 4 to PND 21, and higher doses of ≤1,250 mg/kg/day were well tolerated from PND 22 when the dose levels were escalated to maintain systemic exposure levels up to PND 35, with no observed treatment-related clinical signs, effects on mean body weight gain, or macroscopic findings on articular surfaces. A dose of 1,000 mg/kg/day was not tolerated during the dosing period from PND 4 to 21, with effects on body weight gain, fecal consistency, and body condition. Microscopic effects on articular surfaces were evaluated after 32 days of gepotidacin treatment at the highest tolerated dose. After 32 days of treatment with the highest tolerated gepotidacin dose of 300/1,250 mg/kg/day (systemic concentrations [area under the curve {AUC} values] of 93.7 µg · h/mL [males] and 121 µg · h/mL [females]), no skeletal effects on articular surfaces of the femoral head or stifle joint were observed. The absence of treatment-related clinical signs and arthropathy in juvenile rats provides evidence to support the potential future use of gepotidacin in children.

No developmental toxicity observed with dolutegravir in rat whole embryo culture.

BACKGROUND: An in vitro rat whole embryo culture study investigated whether direct exposure to dolutegravir (TivicayTM ) during the critical period for neural tube development would result in abnormal development. METHODS: Dolutegravir (DTG), and HIV integrase inhibitor, was administered at 0 (vehicle), 5.3 µg/mL and 9.3 µg/mL on Gestation Day (GD) 9 through 11 (approximate 40 hour exposure period) along with positive (Valproic Acid) and negative (Penicillin G) controls. The DTG concentrations tested were selected based on clinical exposure at the maximum human recommended dose and maximum feasible concentration that could be formulated under the experimental conditions. RESULTS: Approximately 6% of DTG present in the culture media was absorbed into the embryos, demonstrating embryonic exposure at a similar level to that observed in a rat DTG placental transfer study. There was no effect in either the DTG or Penicillin G groups on visceral yolk sac size/morphology, embryo size, somite number and embryo morphology at any concentration tested. Valproic Acid, by contrast, produced statistically significant decreases in visceral yolk sac size, embryo size and somite number along with defects in visceral yolk sac and embryonic morphology, including neural tube defects (NTDs), in all embryos. CONCLUSION: DTG at the maximum human recommended dose administered to rats in a whole embryo culture assay did not produce any abnormal effects, while the positive control Valproic Acid produced abnormal effects, including neural tube defects.

Repeated Dose Toxicity Study and Developmental and Reproductive Toxicology Studies of a Respiratory Syncytial Virus Candidate Vaccine in Rabbits and Rats.

Respiratory syncytial virus (RSV) is a leading cause of acute lower respiratory tract infections, and vaccines are needed to treat young children and older adults. One of GSK's candidate vaccines for RSV contains recombinant RSVPreF3 protein maintained in the prefusion conformation. The differences in immune function of young children and older adults potentially require different vaccine approaches. For young children, anti-RSV immunity can be afforded during the first months of life by vaccinating the pregnant mother during the third trimester with unadjuvanted RSVPreF3, which results in protection of the infant due to the transplacental passage of anti-RSV maternal antibodies. For older adults with a waning immune response, the approach is to adjuvant the RSVPreF3 vaccine with AS01 to elicit a more robust immune response.The local and systemic effects of biweekly intramuscular injections of the RSVPreF3 vaccine (unadjuvanted, adjuvanted with AS01, or coadministered with a diphtheria-tetanus-acellular pertussis vaccine) was tested in a repeated dose toxicity study in rabbits. After three intramuscular doses, the only changes observed were those commonly related to a vaccine-elicited inflammatory reaction. Subsequently, the effects of unadjuvanted RSVPreF3 vaccine on female fertility, embryo-fetal, and postnatal development of offspring were evaluated in rats and rabbits. There were no effects on pregnancy, delivery, lactation, or the pre- and postnatal development of offspring.In conclusion, the RSVPreF3 vaccine was well-tolerated locally and systemically and was not associated with any adverse effects on female reproductive function or on the pre- and postnatal growth and development of offspring.

Dose range finding approach for rodent preweaning juvenile animal studies.

OBJECTIVES: Strategies for conducting juvenile dose ranging studies before definitive toxicity juvenile animal studies (JAS) have evolved, but the aim of demonstrating study design robustness and efficient animal use remains the same. The objective of dose selection is to identify a strategy to achieve consistent systemic exposure for the duration of the JAS while maintaining exposure separation between dose groups. For preweaning rodents this can prove challenging, as these studies typically treat animals over a broad period of considerable organ development. MATERIALS AND METHODS: In our experience, over 45 rodent juvenile studies (dose range, definitive or investigative) were conducted over 20 years to support pediatric medicine development. In most cases (86%, 12/14), preweaning rodents required decreased doses of test articles than adult rodents; the majority (83%, 10/12) were due to increased systemic exposures in immature animals at the same doses. Thus, extrapolating tolerability and exposure data from adults is not ideal and should not take the place of well-designed juvenile dose range studies. RESULTS/DISCUSSION/CONCLUSION: We propose a phased dose-range-finding approach by first conducting a tolerability phase with a few animals at a starting age corresponding to the youngest clinical starting age, spanning a wide range of doses, then a dose range phase with larger group sizes and fewer doses; both phases incorporate toxicokinetics. Often, exposure was higher in preweaning animals and decreased as animals matured postweaning (postnatal day, PND 21 and older), supporting an age-based dose adjustment strategy. Case studies demonstrate dose adjustment approaches incorporating dose increases or decreases or changes in dose frequency.

Absence of developmental and reproductive toxicity in animals exposed to dolutegravir.

The success of new antiretroviral medicines for HIV resulted in a change to guidelines of standard therapy where continuation of antiretroviral therapy is recommended to maintain the low viral load during pregnancy, thereby preventing transmission of the virus to the fetus. As a result, pregnancy related exposure to HIV medicines has increased. Understanding the safety of these medicines during pregnancy is of paramount importance to ensure health of mothers and their offspring; well-designed animal studies that evaluate the reproductive life cycle play a key role in this effort. As part of the medicine development program for dolutegravir (DTG), a series of reproductive and developmental toxicity studies were conducted using rats and rabbits. In a fertility study, where exposure to DTG occurred in female rats before mating through conception and up to implantation of the embryo, no effects on reproductive cycles, ovulation, fertility) or preimplantation embryonic growth were observed. In rat and rabbit embryo-fetal development studies, where exposure to DTG occurred during organogenesis, no malformations or other developmental abnormalities were observed. In a rat pre- and post-natal development study, where DTG exposure to the pups occurred during pregnancy and postnatally via milk, no malformations or other developmental abnormalities were observed. In these studies, no DTG-related effects occurred on fertility, embryonic (pre- and post-implantation loss, resorptions, abortions, and malformations) or fetal development where the multiples of exposure at the maximum recommended human dose were up to 27 times higher in rats or below the human exposure in rabbits.

Design and Optimization of Sulfone Pyrrolidine Sulfonamide Antagonists of Transient Receptor Potential Vanilloid-4 with in Vivo Activity in a Pulmonary Edema Model.

Pulmonary edema is a common ailment of heart failure patients and has remained an unmet medical need due to dose-limiting side effects associated with current treatments. Preclinical studies in rodents have suggested that inhibition of transient receptor potential vanilloid-4 (TRPV4) cation channels may offer an alternative-and potentially superior-therapy. Efforts directed toward small-molecule antagonists of the TRPV4 receptor have led to the discovery of a novel sulfone pyrrolidine sulfonamide chemotype exemplified by lead compound 6. Design elements toward the optimization of TRPV4 activity, selectivity, and pharmacokinetic properties are described. Activity of leading exemplars 19 and 27 in an in vivo model suggestive of therapeutic potential is highlighted herein.

Species Comparison of Postnatal Development of the Female Reproductive System.

The postnatal development of the female reproductive system in laboratory animals and humans is reviewed. To enable a meaningful species comparison of the developing female reproductive system, common definitions of developmental processes were established with a focus made on aspects that are similar across species. A species comparison of the key endocrine, morphologic, and functional (onset of ovarian cycles and ability to reproduce) features of postnatal development of the female reproductive system is provided for human, nonhuman primate, dog, rat, and also mouse, minipig, and rabbit where possible. Species differences in the timing and control of female sexual maturation are highlighted. Additionally, a species comparison of the type and timing of female reproductive ovarian cycles was compiled. Human development provided the frame of reference, and then other common laboratory species were compared. The comparison has inherent challenges because the processes involved and sequence of events can differ greatly across species. Broad strokes were taken to assign a particular average age to an event and are to be used with caution. Methods of evaluation of postnatal female reproductive development in laboratory animals are discussed. Lastly, control rodent data from one of the author's laboratory on vaginal opening, first estrus, estrous cyclicity, and the histopathology involved with the developing female rat and mouse are presented. The information provided in this review is intended to be a resource for the design and interpretation of juvenile animal toxicity testing and ultimately, the relevance of the data to characterize potential risks for women and girls. Birth Defects Research 110:163-189, 2018. © 2017 Wiley Periodicals, Inc.

A Probability Analysis of Historical Pregnancy and Fetal Data from Dutch Belted and New Zealand White Rabbit Strains from Embryo-Fetal Development Studies.

Embryo-fetal development (EFD) studies, typically in pregnant rats and rabbits, are conducted prior to enrolling females of reproductive age in clinical trials. Common rabbit strains used are the New Zealand White (NZW) and Dutch Belted (DB). As fetal abnormalities can occur in all groups, including controls, Historical Control Data (HCD) is compiled using data from control groups of EFD studies, and is used along with each study's concurrent control group to help determine whether fetal abnormalities are caused by the test article or are part of background incidences. A probability analysis was conducted on 2014 HCD collected at Charles River Inc., Horsham PA on Covance NZW, Covance DB, and Charles River (CR) NZW rabbits. The analysis was designed to determine the probability of 2 or 3 out of a group of 22 does aborting their litter or of having a fetal abnormality by chance. Results demonstrate that pregnancy parameters and fetal observations differ not only between strains, but between sources of rabbits of the same strain. As a result the probability of these observations occurring by chance in two or three litters was drastically different. Although no one single strain is perfect, this analysis highlights the need to appreciate the inherent differences in pregnancy and fetal abnormalities between strains, and points out that an apparent isolated increased incidence of an observation in one strain will not necessarily be test-article related in another strain. A robust HCD is critical for interpretation of EFD rabbit studies, regardless of the rabbit strain used.

Early Vaginal Opening in Juvenile Female Rats Given BRAF-Inhibitor Dabrafenib Is Not Associated with Early Physiologic Sexual Maturation.

Dabrafenib (DAB), an inhibitor of BRAF kinase activity, is approved for metastatic melanoma with a BRAF V600E mutation. In support of pediatric cancer development, a nonclinical juvenile rat toxicity study was conducted in which females had early vaginal opening (VO). It was hypothesized that the early VO was not indicative of sexual maturation, but a result of a local effect on the vagina. An investigative study was conducted that mimicked the definitive study design, with rats given DAB or vehicle orally from Postnatal Day (PND) 7 to 35 and with necropsy subsets just before VO, at the first and second estrus, along with age-matched controls. Histopathology was performed on reproductive tissues, including immunohistochemistry for BRAF expression. VO occurred earlier in DAB females than in controls (PND 27.2 vs. 31.5); however, the timing of the first estrus was unaffected (PND 34.0 vs. 33.0). DAB-treated females evaluated just before VO (PND 22.0) had mostly immature reproductive tracts with no evidence of ovulation, similar to age-matched controls; however, DAB-treated females had keratinized and histologically open vaginas. Also, there was raised skin around the urogenital area, which correlated with hyperplasia/keratosis of the vulvar skin and keratinization of the distal vagina. BRAF expression (evaluated in controls) was localized to these tissues. Thus, early VO in rats given DAB likely represents a local effect accelerating vaginal keratinization to become open and not accelerated sexual maturation.

Dihydroartemisinin (DHA) treatment causes an arrest of cell division and apoptosis in rat embryonic erythroblasts in whole embryo culture.

Within 24 hr after oral administration of the antimalarial artesunate to rats on Day 10 or 11 postcoitum (pc), there is depletion of embryonic erythroblasts (EEbs), leading to embryo malformation and death. The proximate agent is dihydroartemisinin (DHA), the primary metabolite. We investigated the causes of EEb depletion by evaluating effects of DHA on EEbs in whole embryo culture (WEC). Rat embryos cultured starting on Day 9 pc were treated with 1 or 7 µM DHA for 24 hr starting after 19 hr of culture (∼Day 10 pc) and for 2 to 12 hr starting after 43 hr of culture (∼Day 11 pc). DHA effects indicating the depletion of EEbs were paling of the visceral yolk sac and reductions in visible blood cells, H&E-stained normal (Type II or III) EEbs, and dividing (BrdU-stained) EEbs. DHA-induced abnormal cell division was indicated by increases in symmetric and asymmetric binuclear cells. DHA-induced apoptosis was indicated by increases in TUNEL- and Caspase-3-positive cells and EEbs with fragmented nuclei. In addition, although the overall number of EEbs was decreasing, DHA caused increases in the numbers of circulating early-stage (Type I or earlier) EEbs that could not be accounted for by cell division, suggesting the release of new, less sensitive erythroblasts from the yolk sac. In summary, treatment of Day 10 or 11 pc rat embryos with DHA in WEC resulted in defective and arrested cell division in EEbs followed by apoptosis, suggesting a mechanism for their depletion after artesunate treatment in vivo.

SB-236057: Critical window of sensitivity study and embryopathy of a potent musculoskeletal teratogen.

BACKGROUND: SB-236057 is a potent skeletal teratogen in rodents and rabbits. The study objective was to identify the critical developmental window of compound sensitivity and to characterize the early onset of SB-236057 embryopathy. METHODS: SB-236057 was orally administered to Sprague Dawley dams at 100 mg/kg/day on days 6-7, 8-11, 12-14, or 15-17 postcoitus (pc). The critical window of sensitivity was identified to occur between days 8-11 pc. Dams were then dosed on days 8-11 pc and embryos were evaluated by histochemical procedures on days 11, 13, or 15 pc. RESULTS: Axial malformations were evident by day 11 pc. Analysis of the cartilaginous skeleton revealed missing posterior axial skeletal elements. However, only about one-third of the malformed fetuses exhibited obvious rib and vertebrae abnormalities, and none of the affected fetuses exhibited abnormal appendicular skeletal elements. Expression pattern of sonic hedgehog in the notochord and floor plate was not affected, suggesting ventral midline signaling was not disrupted. Histological analysis demonstrated hypoplastic and/or missing musculature in proximity to the ribs and vertebrae. Caspase 3 analysis revealed no increases in apoptotic cells in the musculature. Confocal analysis of the limbs demonstrated truncated peripheral nerve formation and shortening of the appendicular musculature. CONCLUSIONS: SB-236057 is speculated to alter paraxial mesoderm programming. Many of the skeletal malformations may be caused secondarily from musculature abnormalities, suggesting that the myotome may be particularly sensitive to the compound. Furthermore, the finding that peripheral nerve trajectories were altered along the axis and in the limb suggests that SB-236057 may alter early embryonic signaling pathways necessary for neuronal differentiation/axonal guidance that occur subsequently in embryo-fetal development.