Topical opioid and NSAIDs formulations for the treatment of the peripheral neuropathic pain

1. Topical opioid and NSAIDs formulations Yuri Kolesnikov MD PhD FLAMEK Co

2. Methods and Materials Topical Administration Drugs were applied topically and analgesia was assessed as previously described (Kolesnikov et al., 2000; Kolesnikov et al., 2004). Briefly, the distal portion of the tail (2-3cm) was immersed in propylene glycol/dH 2 O(9:1 ratio) alone or propylene glycol (PG) and a lauric acid (LA) combination (9:1) solution containing the indicated drugs for the stated time, usually 2 min. In our initial studies we have demonstrated that propylene glycol alone has no significant analgesic effect when tested in this manner in the radiant heat tail-flick assay. Furthermore, the addition of lauric acid provides an effective way of solubilizing a wide range of drugs and significantly facilita ting their penetration into the skin . . Radiant Heat Tail-Flick Test Testing was performed on the portion of the tail immersed in the treatment solution, since the analgesic actions of agents administered in this manner are restricted to the exposed part of the tail ( proximal regions are not affected) (Kolesnikov et al., 2000). Analgesia was defined quantally as the tail-flick latency for an individual animal that was twice its baseline latency or greater using tailflick apparatus (Ugo Basile, Italy) . This assay is especially useful in examining topical analgesics, since thermal stimulus usually applies to the superficial surface of the skin, and the thermal energy absorbed in the skin is concentrated in the dermal/epidermal junction where nerve terminals are located. Baseline latencies typically ranged from 2.5 to 3.5 s, with a maximum cutoff latency of 10 s to minimize tissue damage in analgesic animals. Since analgesia was assessed quantally, group comparisons were performed with the Fisher`s exact test (Kolesnikov et al. 1999). ED 50 values were determined with GraphPad Software. Potential interactions between opioids, ibuprophen and diclofenac were assessed using a fixed, low dose of each drug. Groups comparisons were performed with the Fisher`s test.

3. Morphine and Diclofenac Formulation

4. Morphine and S-Ibuprophen Formulation

5. Methadone and Diclofenac Formulation

6. Methadone and S-Ibuprophen Formulation

7. Hydrocodone /diclofenac and hydrocodone /S-ibuprophen formulations

8. Table 1 Addition of lauric acid to propylene glycol enhances the potency of topical drugs in radiant heat tail flick assay Octanol water partition coefficients (OWPC) were derived from Goodman&Gilman. The pharmacological basis of therapeutics. Eleven Edition. 2006 Groups of mice (n ≥ 10) received topical opioids and NSAIDs dissolved either in propylene glycol (PG) alone or in combination with lauric acid(LA) and analgesia was assessed in the tail-flick assay, as described under Methods. At least three doses of the drugs were used to calculate the ED 50 value with 95% CL. Drugs OWPC PG alone PG+LA Shift P value Lidocaine 2.6 2.4 (1.6-3.2)mM 0.35 (0.2-0.42) mM 6.8 <0.0001 Morphine 6.0 7.6 (4.2-10.9)mM 0.40 (0.33-0.54)mM 19 <0.00001 Methadone 117 6.7(4.8-8.8)mM 1.0 (0.8-1.2) mM 6.7 <0.001 Hydrocodone 816 1.6 (1.1-2.2) mM 1.2 (0.8-1.8) mM 1.3 >0.05 S-ibuprophen 12 9.3 (6.1-16.5) mM 2.1 (0.88-3.3) mM 4.4 <0.001 Diclofenac 13.4 3.3 (1.7-5.3) mM 1.1 (0.6-1.78) mM 3.0 < 0.02

9. We next plan is to set the translational study up. Pilot clinical studies have shown, that some opioid /NSAIDs formulations produse analgesia for peripheral neuropathic pain syndrome. The targeted patient population is: Patients with peripheral neuropathic pain syndrome -painful diabetic neuropathie -postherpatic pain syndrome -chronic postsurgical pain -chemotherapie induced neuropathic pain Pilot clinical studies have shown

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