Letters or not, here we come! A communal perspective on credentials needed for a productive career in veterinary pathology.

Veterinary pathology credentials serve as a concise means attesting to educational attainments and experiences indicating a readiness for professional practice. Given the cost, time, and stress associated with obtaining different qualifications, pathologists must consider what credentials enhance their readiness. In this commentary, the authors describe how their various degrees and certifications have facilitated their individual and organizational success. The minimum credentials for proficient veterinary pathology practice are a veterinary medical degree (DVM or equivalent) and advanced pathology training (residency and/or on-the-job "apprenticeship") ideally culminating in board certification in pathology (American College of Veterinary Pathologists [ACVP] diplomate status or equivalent). Graduate degrees (MS, PhD, MPH, etc) and/or other qualifications in allied biomedical fields (eg, board certification in internal medicine, laboratory animal medicine, poultry medicine, preventive medicine, or toxicology) may improve employability by affirming specialty knowledge in another complementary discipline. The authors note that pathology positions may be obtained without a long list of degrees or certifications, and that more credentials may provide occupational flexibility for some employers. However, a good work ethic, experience in the field, ability to adapt to changes, job satisfaction, good attitude, and demonstrated productivity are also important, and indeed, they are often the paramount criteria for career success as a veterinary pathologist.

Re: Re: Laboratory safety evaluation of bedinvetmab, a canine anti-nerve growth factor monoclonal antibody, in dogs.

In their letter to the editor, Farrell et al., (2024) presented questions related to canine joint health after treatment with the anti-Nerve Growth Factor (NGF) monoclonal antibody (mAb) bedinvetmab, which was presented as a component of a non-clinical laboratory safety assessment published in Krautmann et al., (2021). Their questions appear to have stemmed from an anti-NGF mAb developed for the treatment of osteoarthritis in humans (tanezumab; FDA, 2021) which in 2021 failed to achieve marketing approval due to an unfavorable benefit: risk profile, primarily due to a syndrome called Rapidly Progressive Osteoarthritis (RPOA) which occurred more commonly in treatment groups when compared to controls. Farrell et. al. (2024) have posed questions on radiographic and histopathologic bone findings from studies included in Krautmann, et al., (2021) and communicated in the FDA's Freedom of Information summary for Librela (FDA, 2023). These findings have previously been determined to be incidental and not bedinvetmab-associated. To address the questions posed, it is important to briefly define RPOA and summarize the syndrome in humans, review why the bone/joint findings in bedinvetmab safety studies in dogs are not indicative of RPOA or an RPOA-like condition, provide an update on joint health after use of bedinvetmab since market approval (>3 years in some markets), and summarize why Zoetis, the manufacturer of Librela, has confidence in joint safety after use of bedinvetmab in dogs.

Chemotherapy administration directly into the fourth ventricle in a nonhuman primate model.

OBJECT: The authors hypothesized that chemotherapy infusions directly into the fourth ventricle might potentially play a role in treating malignant fourth ventricular tumors. The study tested the safety and pharmacokinetics of short- and long-term infusions of methotrexate into the fourth ventricle in a new nonhuman primate model. METHODS: Six rhesus monkeys underwent posterior fossa craniectomy and catheter insertion into the fourth ventricle. In Group I (3 animals), catheters were externalized, and lumbar drain catheters were placed simultaneously to assess CSF distribution after short-term methotrexate infusions. In 2 animals, methotrexate (0.5 mg) was infused into the fourth ventricle daily for 5 days. Serial CSF and serum methotrexate levels were measured. The third animal had a postoperative neurological deficit, and the experiment was aborted prior to methotrexate administration. In Group II (3 animals), catheters were connected to a subcutaneously placed port for subsequent long-term methotrexate infusions. In 2 animals, 4 cycles of intraventricular methotrexate, each consisting of 4 daily infusions (0.5 mg), were administered over 8 weeks. The third animal received 3 cycles, and then the experiment was terminated due to self-inflicted wound breakdown. All animals underwent detailed neurological evaluations, MRI, and postmortem histological analysis. RESULTS: No neurological deficits were noted after intraventricular methotrexate infusions. Magnetic resonance images demonstrated catheter placement within the fourth ventricle and no signal changes in the brainstem or cerebellum. Histologically, two Group I animals, one of which did not receive methotrexate, had several small focal areas of brainstem injury. Two Group II animals had a small (≤ 1-mm) focus of axonal degeneration in the midbrain. Intraventricular and meningeal inflammation was noted in 4 animals after methotrexate infusions (one from Group I and all three from Group II). In all Group II animals, inflammation extended minimally into brainstem parenchyma. Serum methotrexate levels were undetectable or negligible in both groups, ranging from 0.00 to 0.06 µmol/L. In Group I, the mean peak methotrexate level in fourth ventricle CSF exceeded that in the lumbar CSF by greater than 10-fold. Statistically significant differences between fourth ventricle and lumbar AUC (area under the concentration-time curve) were detected at peaks (p = 0.04) but not at troughs (p = 0.50) or at all time collection points (p = 0.12). In Group II, peak fourth ventricle CSF methotrexate levels ranged from 84.62 to 167.89 µmol/L (mean 115.53 ± 15.95 µmol/L [SD]). Trough levels ranged from 0.06 to 0.55 µmol/L (mean 0.22 ± 0.13 µmol/L). CONCLUSIONS: Methotrexate can be infused into the fourth ventricle in nonhuman primates without clinical or radiographic evidence of injury. Observed inflammatory and other histological changes had no clinical correlate. This approach may have pharmacokinetic advantages over current treatment paradigms. Further experiments are warranted to determine if fourth ventricular chemotherapy infusions may benefit patients with malignant fourth ventricular tumors.

The Safety of EXPAREL ® (Bupivacaine Liposome Injectable Suspension) Administered by Peripheral Nerve Block in Rabbits and Dogs.

A sustained-release DepoFoam injection formulation of bupivacaine (EXPAREL, 15 mg/mL) is currently being investigated for postsurgical analgesia via peripheral nerve block (PNB). Single-dose toxicology studies of EXPAREL (9, 18, and 30 mg/kg), bupivacaine solution (Bsol, 9 mg/kg), and saline injected around the brachial plexus nerve bundle were performed in rabbits and dogs. The endpoints included clinical pathology, pharmacokinetics, and histopathology evaluation on Day 3 and Day 15 (2/sex/group/period). EXPAREL resulted in a nearly 4-fold lower C(max) versus Bsol at the same dose. EXPAREL was well tolerated at doses up to 30 mg/kg. The only EXPAREL-related effect seen was minimal to mild granulomatous inflammation of adipose tissue around nerve roots (8 of 24 rabbits and 7 of 24 dogs) in the brachial plexus sites. The results indicate that EXPAREL was well tolerated in these models and did not produce nerve damage after PNB in rabbits and dogs.

The safety and tolerability evaluation of DepoFoam bupivacaine (bupivacaine extended-release liposome injection) administered by incision wound infiltration in rabbits and dogs.

OBJECTIVE: DepoFoam bupivacaine (DB) is in development for prolonged postoperative analgesia. Studies were conducted to evaluate the potential local and systemic toxicity and any effect on wound healing after wound infiltration. METHODS: The model simulates an inguinal hernia (skin incision ∼2.5 and 5.5 cm). Animals (four/sex/group of each species) received DB 9, 18 or either 25 or 30 mg/kg, bupivacaine solution (B(sol); 7.5 mg/ml, 9 mg/kg) or saline. DB was given at 0.6, 1.2 and 1.0 or 1.2 ml/kg, respectively, and B(sol) or saline at 1.2 ml/kg. Each dose was infiltrated in small fractions on Day 1. End points included histology on Days 3 and 15. Wound healing was recorded on Day 2 through Day 15. RESULTS: There was no adverse effect in either species. Notably, granulomatous inflammation was noted in surgical sites from 8 of 24 rabbits in the DB groups only. Based on the minimal to mild severity on Day 15, this was considered a normal reaction against the liposomes. Except for granulomatous inflammation, there were no differences in overall incidence or severity of histologic changes in the sites dosed to DB, saline or B(sol). CONCLUSIONS: The data reported here are the first demonstration of the safety of DB in toxicology species.

Studies of the pharmacology of 17α-ethynyl-androst-5-ene-3ß,7ß,17ß-triol, a synthetic anti-inflammatory androstene.

17α-Ethynyl-androst-5ene-3ß, 7ß, 17ß-triol (HE3286) is an orally bioavailable analogue of androst-5-ene-3ß,7ß,17ß-triol, a non-glucocorticoid anti-inflammatory metabolite of the adrenal steroid, dehydroepiandrosterone. The pharmacology of HE3286 was characterized in preparation for clinical trials in type 2 diabetes mellitus and other diseases of inflammation. Interactions with nuclear hormone receptors and P450 enzymes were measured in vitro. Drug metabolism was studied preclinically in mice, rats, dogs, and monkeys. Neurological and cardiopulmonary safety and dose-ranging and chronic toxicity studies were conducted in rats and dogs in accordance with FDA guidelines. Pharmacokinetics and metabolites were measured in Phase I clinical trials. HE3286 was differentially metabolized between species. HE3286 and metabolites did not bind or transactivate steroid binding nuclear hormone receptors or inhibit P450 enzymes. There were no adverse effects in safety pharmacology and canine toxicology studies. Although HE3286 did not elicit systemic toxicity in rats, mild estrogenic effects were observed, but without apparent association to hormonal changes. Safety margins were greater than 20-fold in rats and dogs with respect to the most commonly used clinical dose of 10 mg/day. The terminal half-life in humans was 8 hours in males and 5.5 hours in females. HE3286 is the first derivative of the DHEA metabolome to undergo a comprehensive pharmacological and safety evaluation. The results of these investigations have shown that HE3286 has a low potential for toxicity and possesses pharmacological properties generally suitable for use in human medicine. The favorable profile of HE3286 warrants further exploration of this new class of anti-inflammatory agents.

Safety Evaluation of EXPAREL (DepoFoam Bupivacaine) Administered by Repeated Subcutaneous Injection in Rabbits and Dogs: Species Comparison.

EXPAREL (bupivacaine extended-release liposome injection), DepoFoam bupivacaine, is in development for prolonged postsurgical analgesia. Repeat-dose toxicity studies were conducted in rabbits and dogs to compare the potential local and systemic toxicities of EXPAREL and bupivacaine HCl (Bsol), and the reversibility of any effects. Dogs tolerated much larger doses than rabbits. EXPAREL-related minimal-to-moderate granulomatous inflammation was noted at the injection sites. In recovery animals, the granulomatous inflammation was observed less frequently and was characterized by an increased number of multinucleated giant cells. These effects were considered a normal response to liposomes and nonadverse. Rabbits are more sensitive than dogs. In rabbits, convulsions were noted with EXPAREL and more frequently with Bsol; a NOAEL was not identified. In dogs, EXPAREL was well tolerated (NOAEL > 30 mg/kg/dose). The cumulative exposure of EXPAREL in these studies is well in excess of the proposed maximum single-dose exposure that is intended in humans.