Refinement, Reduction, and Replacement (3R) Strategies in Preclinical Testing of Medical Devices

The U.S. Food and Drug Administration Center for Devices and Radiological Health (FDA/CDRH) has recently published several in vivo test guidance documents that mention refinements, reductions, or replacement animal testing strategies to facilitate the leveraging of data from large animal safety tests for conventional rodent testing. In response to the recently enacted Food and Drug Administration Safety and Innovation Act Section 907, which facilitates expedited access to novel therapies commonly described as Breakthrough Therapy Designation, FDA/CDRH has discussed efficient regulatory strategies for first-in-human investigation, including early feasibility study guidance. Large gains in humane care and translational research could also be attained by examples in FDA's Guidance for the Use of International Organization for Standardization 10993-1, which states that large animal safety studies may be considered as replacement rodent tests if the scientific principles, methods, and end points (SPME) are considered and applied. This article discusses SPME for the replacement of conventional rodent testing by the inclusion and integration of clinical, diagnostic, and pathologic data obtained from well-designed large animal studies. The recommendations include consideration for study designs that utilize methods for an overall more comprehensive interrogation of animal systems.

Report of the Working Group on Animal Distress in the Laboratory

Finding ways to minimize pain and distress in research animals is a continuing goal in the laboratory animal research field. Pain and distress, however, are not synonymous, and measures that alleviate one may not affect the other. Here, the authors provide a summary of a meeting held in February 2004 that focused on distress in laboratory animals. They discuss the difficulties associated with defining 'distress,' propose methods to aid in recognizing and alleviating distressful conditions, and provide recommendations for animal research conduct and oversight that would minimize distress experienced by laboratory animals.

Evaluation of efficacy of heartworm preventive products at the FDA

The Center for Veterinary Medicine, U.S. Food and Drug Administration (FDA/CVM) has authority under the United States Code 21 under Section 514.80 to monitor for adverse experiences of approved animal products. Although veterinarians voluntarily report suspect drug-related events to manufacturers, firms that market FDA-approved animal products must report serious events to the FDA within 15 working days of the veterinarian or pet-owner's call to them. Under the present regulations, canine heartworm preventatives are approved for 100% efficacy after testing in laboratory and field conditions. The report of lack of efficacy against heartworm larvae is a serious adverse drug event because the resulting condition or the treatment of the condition is life threatening. Information on lack of effect that are deemed possibly, probably, or definitely drug-related available for review under generic product on the FDA/CVM website Surveillance of these reports indicates there are some failures for virtually all heartworm prevention product categories. Most failures have been reported in heartworm-endemic states. At this time, it is unclear whether these are representative of the rare occurrences of failure that have been in existence for a long time, but not reported regularly or promptly, or whether there is a true increase in complaints of ineffectiveness and real variability between products. This paper discusses methods, personnel, and procedures in place in the Division of Surveillance that will aid the FDA to better assess heartworm preventive treatment failures. It discusses scoring paradigms presently utilized by FDA/CVM to assess severity of complaints of lack of efficacy against heartworms, and welcomes audience input as to how to improve existing processes. Results suggest that more comprehensive reporting will provide FDA/CVM more accurate surveillance information regarding efficacy problems. Such practices will permit FDA/CVM to better interpret both incidence and severity of in-effect and possible patterns of emerging resistance and to convey this in any necessary updated labeling. It also indicates that as part of that process, practitioners should return to a more conservative testing schedule.

Regulatory issues surrounding the use of companion animals in clinical investigations, trials, and studies

Laboratory animal veterinarians sometimes encounter animals with rare conditions and may subsequently become involved in the performance of related animal research outside the laboratory, in homes, in veterinary clinics, or in universities to which owners have donated their animals for study. Similarly, veterinarians may monitor animal companion vaccination studies, performed to optimize preventive health care or minimize physiological variability and research confounders associated with a preventive medicine program for dogs and cats utilized for research procedures. These nontraditional uses of dogs, cats, and other companion animals in research have spurred the establishment of regulations to ensure that the animals benefit from clinical veterinary products and techniques. Included and described are the 2002 Public Health Service Policy, the Animal Welfare Act (AWA), the Federal Food, Drug, and Cosmetic Act, and the regulations of the US Department of Agriculture in response to the AWA. The complexities of clinical research with companion animals outside standard biomedical research facilities are discussed.

Challenges in small animal noninvasive imaging

The current status and challenges of small animal non-invasive imaging is briefly reviewed. The advantages of non-invasive studies on living animals versus post-mortem studies are evaluated. An argument is advanced that even in post-mortem situations, non-invasive imaging may play an important role in efficiently characterizing small animal phenotypes as well as pathology. Issues of data interpretation under anesthetized conditions in live animal studies are also reviewed. The five imaging technologies covered include CT, PET, ultrasound, MRI and optical imaging. The structural and physiological information content of these different modalities is reviewed along with the ability of these techniques to scale down for use in small mammals such as mice and rats. In general, it was found that most of these technologies scale favorably to the study of small mammals, generally providing more physiological information than when used on the larger human scale. This suggests that these types of small mammal imaging capabilities will play a very significant role in the full utilization of these important animal models in biomedical research.

Retrospective comparison of rat recovery weights using inhalation and injectable anaesthetics, nutritional and fluid supplementation for right unilateral neurosurgical lesioning

Current veterinary standards of biomedical research support include refinements in animal models that are targeted at enhancing humane care and decreasing inter-animal variability. This ultimately results in fewer numbers of animals being used and reduction in animal experimentation through mitigation of waste as well as faster research results. 6-hydroxydopamine-lesioning of the substantia nigra using a stereotactic frame device is a common procedure and is routinely performed under pentobarbital anaesthesia with monitoring by 8 h workforces. Our programme supports the humane care and use of several protocols involving the unilateral stereotactic-lesioning of rats for the purposes of creating research models of Parkinsonianism. Such procedures are commonly performed as unilateral in order to minimize aphagia and other untoward effects of the lesion. Generally, this procedure is considered minor because it involves a small incision, a cranial burrhole, and penetration of the dura. Inflammation and/or irritation of the ear canal can occur secondarily to the earbar placement procedure. Human patients undergoing similar procedures typically complain of headaches from loss of intracranial pressure; which is a transient outcome. Despite the perception of minor insult, we provided aggressive periprocedural care, and our veterinary staff documented weight loss that was often greater than 15% body weight during the first 3 days. The goal of this study was to evaluate refinements to improve this outcome. For humane concerns, and because of the need to begin experimental testing one week following surgery, a goal in the recent past has been to enhance outcome for researchers and animals by refining postoperative support modalities as well as by seeking the best anaesthetic regimen to shorten postoperative deviations from baseline. Analysis of three groups of rat patients lesioned by the same investigative group over the course of refinements made in our programme indicate that an early return of homeostasis was achieved by the use of inhalation anaesthetics as replacements for barbiturates in these models. Comparison with pentobarbital recipients also indicated that homeostasis is achieved earlier when barbiturates are utilized with fluid therapy and analgesics immediately after operative procedures rather than the next morning.

Thoracoscopy as a nonpharmacotherapeutic research modification for limiting postoperative chest pain

Diminished tissue injury and shortened clinical recovery are benefits of using an endoscopic approach for patients needing operative procedure. In the course of developing an experimental model requiring procurement of topographically precise lung biopsy specimens, we sought to apply thoracoscopy as a research alternative to thoracotomy. In addition, we investigated the influence of thoracoscopy on postprocedure recovery practices using rabbits divided into four treatment groups. Rabbit groups 1 and 2 underwent thoracoscopy and lung biopsy while maintained by one-lung anesthesia. Additionally, group 2 had ketoprofen and bupivacaine HCl analgesics injected for treatment during postprocedure recovery. These two groups were compared to control rabbits in groups 3 and 4, which underwent inhalant anesthesia without thoracoscopy. Control group 3 also received the injection analgesic combination. During recovery, rabbit behavior was systematically assessed for evidence of pain. No behavior considered indicative of pain needing intervention was observed regardless of treatment group. Limited changes in plasma corticosterone, catecholamines, and prostaglandin E2 levels measured during recovery were difficult to associate with any treatment. Unexpectedly, significantly different mean corticosterone and catecholamines levels were detected in rabbits given the injection analgesic combination in the absence of thoracoscopic procedure, as compared to other treatment groups. The results highlight the importance of awareness that analgesic drug administration has the potential to alter homeostasis and affect interpretation of some study findings by its own guise. Correlation of the mean pain study results with plasma biochemical data supports preferential use of thoracoscopy as a refinement for limiting postprocedural pain in research models.

Clinical toxicity of peripheral nerve to intraoperative radiotherapy in a canine model

PURPOSE

The clinical late effects of intraoperative radiotherapy (IORT) on peripheral nerve were investigated in a foxhound model.

METHODS AND MATERIALS

Between 1982 and 1987, 40 animals underwent laparotomy with intraoperative radiotherapy of doses from 0-75 Gy administered to the right lumbosacral plexus. Subsequently, all animals were monitored closely and sacrificed to assess clinical effects to peripheral nerve. This analysis reports final clinical results of all animals, with follow-up to 5 years.

RESULTS

All animals treated with > or = 25 Gy developed ipsilateral neuropathy. An inverse relationship was noted between intraoperative radiotherapy dose and time to neuropathy, with an effective dose for 50% paralysis (ED50) of 17.2 Gy. One of the animals treated with 15 Gy IORT developed paralysis, after a much longer latency than the other animals.

CONCLUSIONS

Doses of 15 Gy delivered intraoperatively may be accompanied by peripheral neuropathy with long-term follow-up. This threshold is less than that reported with shorter follow-up. The value of ED50 determined here is in keeping with data from other animal trials, and from clinical trials in humans.

Effects of intraoperative radiotherapy on vascular grafts in a canine model

PURPOSE

The effects of intraoperative radiotherapy +/- external beam radiotherapy on prosthetic vascular grafts were investigated in a canine model.

METHODS AND MATERIALS

In 1986 and 1987, 30 adult beagles underwent laparotomy with transection and segmental resection of the infrarenal aorta followed by immediate reconstruction with a prosthetic graft. Intraoperative radiotherapy at varying doses from 0-30 Gy was then administered to all animals. Half of the dogs received 36 Gy external beam radiotherapy in 10 fractions postoperatively. Animals were sacrificed and necropsied at predetermined intervals and as clinically indicated to assess early (< or = 6 months) and late (> 6 months) effects to the vascular graft and surrounding normal tissue.

RESULTS

Histopathologic analyses of irradiated vascular structures were performed and correlations were made with the clinical outcome. The most frequent early clinical toxicity was graft thrombosis, occurring in 7 of 10 animals followed for < or = 6 months. Early graft thrombus formation appeared unrelated to radiotherapy dose and probably represented a technical surgical complication. Anastomotic stenosis of varying severity occurred in most animals followed > 6 months. Late (> 6 months) graft stenosis was correlated with intraoperative radiotherapy dose. At < or = 20 Gy of intraoperative irradiation, 3 of 14 animals developed late graft occlusion; at > 25 Gy, five of six animals developed late occlusion. On histopathologic review, increasing intraoperative dose and increasing total radiotherapy dose (intraoperative+external beam) appeared to correspond with increasing severity of graft changes seen after 6 months of follow-up.

CONCLUSIONS

Thrombus formation is a frequent early complication of vascular graft placement of the infrarenal aorta in our beagle dog model. Intraoperative doses up to 20 Gy appear to contribute minimally to late graft occlusion, while doses > or = 25 Gy contribute to late occlusion with high likelihood. Both intraoperative dose and total radiotherapy dose correlated with late graft occlusion, and with histopathologic changes in the graft and anastomoses.

Hemodynamics and metabolism during surface-induced hypothermia in the dog: a comparison of pH management strategies

The management of blood pH during hypothermia remains controversial. The present study was designed to determine whether hemodynamics and oxygen consumption during hypothermia are different between the alpha-stat and pH-stat strategies. Theoretical considerations of enzyme kinetics suggest that the alpha-stat strategy would result in a higher oxygen consumption during hypothermia. Because hypothermia is used to decrease oxygen consumption for protection during ischemia, a pH scheme that results in a greater oxygen demand for any level of ischemia would be detrimental. The core temperature of 22 dogs was lowered to 26 degrees C by combined surface cooling and gastric irrigation. Either the alpha-stat (N = 9) or the pH-stat (N = 13) pH strategy was used. The arterial pressure was different between the two groups at 26 degrees C (65 +/- 6 vs 85 +/- 6 mm Hg, alpha-stat vs pH-stat, respectively, P less than 0.05). Neither systemic oxygen consumption nor the Q10 was different between groups. There were no differences in any other hemodynamic parameters. In summary, during moderate hypothermia alpha-stat pH management results in an arterial pressure lower than that of pH-stat management, possibly resulting in improved peripheral perfusion. Despite theoretical predictions, the alpha-stat pH scheme does not result in an oxygen consumption higher than that of the pH-stat scheme.