Management of adverse side-effects after chemotherapy in macaques as exemplified by streptozotocin: case studies and recommendations.

The chemotherapeutic streptozotocin is used for induction of diabetes in animal models including non-human primates. Being a cytotoxic nitrosourea compound, it can be associated with adverse events (AEs), mainly nausea and emesis, nephrotoxicity, elevated liver transaminase levels, pulmonary oedema and, most prominently, metabolic acidosis: these can be severe in some cases. The incidence and gravity are to some extent related to the characteristics of the individual animal, diagnostic tools, prompt recognition of symptoms and supportive measures. Careful animal selection, dose adaptation and supportive actions such as renal protective hydration are the main tools in managing AEs, but do not fully eliminate unavoidable and sometimes life-threatening conditions. In our centre we have built experience in a cohort of 78 cynomolgus and rhesus macaques in which six cases manifested severe AEs (8%). This experience has prompted implementation of strategies for early detection and management of adverse effects, together with an animal refinement programme. We present here specific pretreatment regimens, post-infusion laboratory evaluations, and flow charts to assess/treat metabolic acidosis and precipitating factors. Case reports of the six animals with severe AEs are presented to illustrate management of AEs, especially metabolic acidosis, and criteria for early euthanasia where appropriate. We conclude that improved monitoring and validated tools allow for optimal management of adverse effects in an early stage of their manifestation. Reduced morbidity and mortality not only improve individual animal wellbeing but also avoid model-induced confounding that diminishes the translational value of the experimental protocol.

Successful implementation of cooperative handling eliminates the need for restraint in a complex non-human primate disease model.

BACKGROUND: Streptozotocin-induced diabetic non-human primates are used to study efficacy and safety of innovative immunosuppression after islet transplantation. We implemented a training program for medical management of a chronic disease state. METHODS: Cooperation with hand feeding and drinking, shifting, and limb presentation were trained utilizing predominately positive but also negative reinforcement in 52 animals compared with 28 macaques subjected to conventional physical and/or chemical restraint. The success and timing of behavior acquisition was evaluated in a representative subset of 14 animals. RESULTS: Over 90% of animals were successful in behavior acquisition. Programmatically this resulted in complete elimination of chair restraint and negligible requirement for sedation. About half of the trained animals had no-to-moderate thymic involution, indicative of a substantial reduction in stress. CONCLUSION: Cooperative handling enhances animal well-being. This contributes to validity of scientific results and eliminates model-induced confounding that can obstruct interpretation of safety and efficacy data.

Refining the high-dose streptozotocin-induced diabetic non-human primate model: an evaluation of risk factors and outcomes.

In preparation for islet transplantation, diabetes was induced using streptozotocin (STZ) in non-human primates ranging from juveniles to adults with diverse body types: we studied the process with respect to the diabetic state and emergence of adverse events (AEs) and their severity, and identified risk factors for clinical and laboratory AEs. Pharmaceutical-grade STZ was given based on body surface area (BSA) (1050-1250 mg/m(2), equivalent to 80-108 mg/kg) or on body weight (BW) (100 mg/kg) to 54 cynomolgus and 24 rhesus macaques. AEs were related to risk factors, i.e. obesity parameters, BW and BSA, age and STZ dose in mg/m(2). Clinical AEs during the first days after infusion prompted euthanasia of three animals. Except for those three animals, diabetes was successfully induced as shown by circulating C-peptide levels, the intravenous glucose tolerance test and/or arginine stimulation test. C-peptide after infusion weakly correlated (P = 0.048) with STZ dose in mg/m(2). Grade ≥3 nephrotoxicity or hepatotoxicity (serum markers >3× baseline or >5 × baseline, respectively) occurred in about 10% of cases and were generally mild and reversible. Grade ≥2 clinical AEs occurred in seven of 78 animals, reversed in four cases and significantly correlated with obesity parameters. Taking girth-to-height ratio (GHtR) as an indicator of obesity, with threshold value 0.92-0.95, the positive predictive value of obesity for AEs was 92% and the specificity 94%. We conclude that diabetes is successfully induced in non-obese animals using a 100 mg/kg pharmaceutical grade STZ dose. Obesity is a significant risk factor, and animals with a higher than normal GHtR should preferably receive a lower dose. The incidence of relevant clinical or laboratory AEs is low. Careful monitoring and supportive medical intervention can result in recovery of AEs.

Long-term hepatic vascular access in the nonhuman primate for recurrent portal vein infusion.

Islet cell transplantation in nonhuman primates is generally performed in the liver, by infusion of the transplant into the portal vein. We introduced a vascular access port with the catheter tip located in the splenic vein to avoid multiple major survival surgeries. This procedure was conducted in 16 cynomolgus and 9 rhesus macaques. A subset underwent islet cell transplantation. A historic control group (n = 17) received the transplant via open midline laparotomy. The groups did not differ in operation time (median about 60 min): however, animals undergoing midline laparotomy required significantly more opioid pain relief postoperatively than animals implanted with a hepatic vascular access port. Animals after port placement and transplantation had significantly higher blood hemoglobin values than those in the control group, but these values were still in the normal range. In addition to transplantation, the port could be used for administration of biologics and for blood sampling. In all cases, the port remained patent for infusion purposes (median follow-up 336 days, range 62-485 days). Patency for blood sampling was maintained in about half of the animals: the 50% survival of patency for sampling was 255 days. This difference between infusion and sampling patency is most likely due to the location of the catheter tip in the splenic vein, with occlusion caused by the small vessel-to-catheter ratio. We conclude that hepatic vascular access enables long-term frequent administration of cells, medication, or other products and also serves to sample blood: hence, this procedure contributes to a higher level of animal's well-being.

Refinement of vascular access port placement in nonhuman primates: complication rates and outcomes.

Chronic vascular access is often needed in experimental animal studies, and vascular access ports (VAP) have been proposed as an alternative to conventional venipuncture. We previously reported on VAP implantation by using femoral venous cutdown (FVC) and tunneling. In an attempt to decrease the moderate complications associated with the FVC method, we developed the single-incision, peripheral-insertion (SIPI) method. In a retrospective evaluation, 92 FVC procedures were compared with 113 SIPI procedures in cynomolgus and rhesus macaques and baboons with as much as 2.5 y of follow-up. The rate of complications was significantly lower for the SIPI method than for the FVC method (19.4% versus 33.7%), particularly in regard to infectious complications (8.0% versus 27.3%, respectively). In addition, VAP patency for blood sampling and fluid infusion was significantly better for the SIPI method than for the FVC method, with 1-y patency rate of 83% and 46%, respectively, and 2-y patency rate of 74% and 36%, respectively. Additional advantages of the SIPI method include the simplified implantation of the VAP and access in the homecage without any sedation or restraint after appropriate training of animals to cooperate. We conclude that the SIPI method presents an opportunity for refinement and is superior to the FVC method for chronic vascular access.

A novel alternative placement site and technique for totally implantable vascular access ports in non-human primates.

BACKGROUND: Two novel approaches to implanting a central venous catheter port in non-human primates (NHPs) using peripheral insertion are presented and compared. METHODS: Sixty vascular access port (VAP) implants were attempted in 52 NHPs by saphenous vein puncture (n = 20) or saphenous vein cutdown (n = 40). RESULTS: Fifty eight procedures were successful. Eighteen of 20 VAPs were successfully placed using saphenous vein puncture, and 40 of 40 using saphenous vein cutdown. There were no significant differences between procedures. Mean implantation times were similar between groups. At explant or study endpoint, all 58 VAPs were patent. CONCLUSIONS: Vascular access port implantation by saphenous vein puncture or saphenous vein cutdown is safe and effective in NHPs. It is less invasive than conventional procedures, has fewer complications, provides outstanding patency, and reduces surgery time. Furthermore, it allows for cooperative in-homecage VAP use, minimizing handling stress. We recommend these refined methods for long-term vascular access in NHPs.