Comparative analgesic efficacy of pregabalin administered according to either a prevention protocol or an intervention protocol in rats with cisplatin‐induced peripheral neuropathy

Animal Models of Cancer-Related Pain: Current Perspectives in Translation

The incidence of pain in cancer patients during diagnosis and treatment is exceedingly high. Although advances in cancer detection and therapy have improved patient prognosis, cancer and its treatment-associated pain have gained clinical prominence. The biological mechanisms involved in cancer-related pain are multifactorial; different processes for pain may be responsible depending on the type and anatomic location of cancer. Animal models of cancer-related pain have provided mechanistic insights into the development and process of pain under a dynamic molecular environment. However, while cancer-evoked nociceptive responses in animals reflect some of the patients’ symptoms, the current models have failed to address the complexity of interactions within the natural disease state. Although there has been a recent convergence of the investigation of carcinogenesis and pain neurobiology, identification of new targets for novel therapies to treat cancer-related pain requires standardization of methodologies within the cancer pain field as well as across disciplines. Limited success of translation from preclinical studies to the clinic may be due to our poor understanding of the crosstalk between cancer cells and their microenvironment (e.g., sensory neurons, infiltrating immune cells, stromal cells etc.). This relatively new line of inquiry also highlights the broader limitations in translatability and interpretation of basic cancer pain research. The goal of this review is to summarize recent findings in cancer pain based on preclinical animal models, discuss the translational benefit of these discoveries, and propose considerations for future translational models of cancer pain.

Recent advances in understanding chemotherapy-induced peripheral neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN) is a common cause of pain and poor quality of life for those undergoing treatment for cancer and those surviving cancer. Many advances have been made in the pre-clinical science; despite this, these findings have not been translated into novel preventative measures and treatments for CIPN. This review aims to give an update on the pre-clinical science, preventative measures, assessment and treatment of CIPN.

Somatosensory predictors of response to pregabalin in painful chemotherapy-induced peripheral neuropathy: a randomized, placebo-controlled, crossover study

Painful chemotherapy-induced peripheral neuropathy (CIPN) is a debilitating and treatment-resistant sequela of many chemotherapeutic medications. Ligands of α2δ subunits of voltage-gated Ca channels, such as pregabalin, have shown efficacy in reducing mechanical sensitivity in animal models of neuropathic pain. In addition, some data suggest that pregabalin may be more efficacious in relieving neuropathic pain in subjects with increased sensitivity to pinprick. We hypothesized that greater mechanical sensitivity, as quantified by decreased mechanical pain threshold at the feet, would be predictive of a greater reduction in average daily pain in response to pregabalin vs placebo. In a prospective, randomized, double-blinded study, 26 patients with painful CIPN from oxaliplatin, docetaxel, or paclitaxel received 28-day treatment with pregabalin (titrated to maximum dose 600 mg per day) and placebo in crossover design. Twenty-three participants were eligible for efficacy analysis. Mechanical pain threshold was not significantly correlated with reduction in average pain (P = 0.97) or worst pain (P = 0.60) in response to pregabalin. There was no significant difference between pregabalin and placebo in reducing average daily pain (22.5% vs 10.7%, P = 0.23) or worst pain (29.2% vs 16.0%, P = 0.13) from baseline. Post hoc analysis of patients with CIPN caused by oxaliplatin (n = 18) demonstrated a larger reduction in worst pain with pregabalin than with placebo (35.4% vs 14.6%, P = 0.04). In summary, baseline mechanical pain threshold tested on dorsal feet did not meaningfully predict the analgesic response to pregabalin in painful CIPN.

Searching for analgesic drug candidates alleviating oxaliplatin-induced cold hypersensitivity in mice

Oxaliplatin is a third-generation, platinum-based derivative used to treat advanced colorectal cancer. Within the patient population on oxaliplatin therapy, a lower incidence of hematological adverse effects and gastrointestinal toxicity is noted, but severe neuropathic pain episodes characterized by increased cold and tactile hypersensitivity are present in ~95% of patients. This drug is also used to induce a rodent model of chemotherapy-induced peripheral neuropathy (CIPN)-related neuropathic pain which is widely used in the search for novel therapies for CIPN prevention and treatment. This paper provides a step-by-step, detailed description of the prevention and intervention protocols used in our laboratory for the assessment of oxaliplatin-induced cold allodynia in mice. To establish cold sensitivity in mice, the cold plate test was used. Latencies to pain reaction in response to cold stimulus (2.5°C) for vehicle-treated non-neuropathic mice, vehicle-treated mice injected with oxaliplatin (neuropathic control), and oxaliplatin-treated mice treated additionally with duloxetine are compared. Duloxetine is a serotonin/noradrenaline reuptake inhibitor which was found to produce significant pain relief in patients with CIPN symptoms. In our present study, duloxetine administered intraperitoneally at the dose of 30 mg/kg served as a model antiallodynic drug which attenuated or partially prevented cold allodynia caused by oxaliplatin.

Interventional and preventive effects of aripiprazole and ceftriaxone used alone or in combination on oxaliplatin-induced tactile and cold allodynia in mice

BACKGROUND AND PURPOSE

Chemotherapy-induced peripheral neuropathy (CIPN) is a pharmacoresistant neurological complication induced by some antitumor drugs. This study aimed to assess antiallodynic properties of aripiprazole and ceftriaxone used alone or in combination to attenuate neuropathic pain related to CIPN caused by oxaliplatin.

METHODS

Neuropathic pain was induced in mice by a single intraperitoneal dose of oxaliplatin (10 mg/kg). Aripiprazole and ceftriaxone were used in a single- or repeated dosing protocol. Their antiallodynic activity was assessed using von Frey and cold plate tests on the day of oxaliplatin injection and after 7 days. The influence of aripiprazole and ceftriaxone on animals' locomotor activity and motor coordination was also assessed.

RESULTS

Single-dose and repeated-dose aripiprazole 10 mg/kg and ceftriaxone 200 mg/kg used alone and in combination attenuated early-phase and late-phase tactile allodynia in oxaliplatin-treated mice. Repeated administrations of ceftriaxone 200 mg/kg prevented the development of late-phase tactile allodynia. Both drugs showed no antiallodynic properties in the cold plate test. Single-dose aripiprazole 1 and 10 mg/kg but not its repeated administration significantly decreased locomotor activity of oxaliplatin-treated mice. Single-dose aripiprazole 1 and 10 mg/kg, aripiprazole 1 mg/kg + ceftriaxone 50 mg/kg and aripiprazole 1 mg/kg + ceftriaxone 200 mg/kg impaired motor coordination in the rotarod test.

CONCLUSIONS

In mice, neither ceftriaxone nor aripiprazole attenuated cold allodynia. Ceftriaxone alone could attenuate tactile allodynia caused by oxaliplatin without inducing motor adverse effects. Although the administration of aripiprazole reduced tactile allodynia, this effect seems to be limited considering severe motor deficits induced by this drug.

Novel amide derivatives of 1,3-dimethyl-2,6-dioxopurin-7-yl-alkylcarboxylic acids as multifunctional TRPA1 antagonists and PDE4/7 inhibitors: A new approach for the treatment of pain

A series of novel amide derivatives of 1,3-dimethyl-2,6-dioxopurin-7-yl-alkylcarboxylic acids designed using a structure-based computational approach was synthesized and assayed to evaluate their ability to block human TRPA1 channel and inhibit PDE4B/7A activity. We identified compounds 16 and 27 which showed higher potency against TRPA1 compared to HC-030031. In turn, compound 36 was the most promising multifunctional TRPA1 antagonist and PDE4B/7A dual inhibitor with IC₅₀ values in the range of that of the reference rolipram and BRL-50481, respectively. Compound 36 as a combined TRPA1/PDE4B/PDE7A ligand was characterized by a distinct binding mode in comparison to 16 and 27, in the given protein targets. The inhibition of both cAMP-specific PDE isoenzymes resulted in a strong anti-TNF-α effect of 36in vivo. Moreover, the potent anti-inflammatory and analgesic efficacy of 36 was observed in animal models of pain and inflammation (formalin test in mice and carrageenan-induced paw edema in rats). This compound also displayed significant antiallodynic properties in the early phase of chemotherapy-induced peripheral neuropathy in mice. In turn, the pure TRPA1 antagonists 16 and 27 revealed a statistically significant antiallodynic effect in the formalin test and in the von Frey test performed in both phases of oxaliplatin-induced allodynia. Antiallodynic activity of the test compounds 16, 27 and 36 was observed at a dose range comparable to that of the reference drug - pregabalin. In conclusion, the proposed approach of pain treatment based on the concomitant blocking of TRPA1 channel and PDE4B/7A inhibitory activity appears to be interesting research direction for the future search for novel analgesics.