Other than its potential to avoid most of the the problems inherent in the use of systemically delivered opioids, one thing that particularly impresses me about the TPM/ Oxycodone patch is the wide range of indications for which it might be suitable. Multiple indications for a product reduces development risk and maximises potential returns.
As the company states, if the TPM/Oxycodone patch is found to be effective in treating post-herpetic neuralgia, it is likely to also be suitable for treating other forms of neuropathic pain. Diabetic peripheral neuropathy and HIV-induced neuropathy are suggested as other possible neuropathic pain conditions in today's release.The broader neuropathic pain market is substantial in size - as stated by the company, neuropathic pain generates $4 billion in sales annually in the United States alone. (IMS Health)
The TPM/Oxycodone patch might also be suitable for the localised pain conditions of osteoarthritis and lower back pain. Osteoarthritis and lower back pain are not only significant markets , both conditions have been identified as priorities for pharmaceutical research for 2014 to 2020 by the World Health Organization, based on the Global Burden of Disease Database. (1)
Additionally, the topical patch might be suitable for the lower-profile localised pain condition of post-surgical pain. I was prompted to do some research on chronic post-surgical pain (CPSP, also known as persistent postsurgical pain, PPP) after a family member had surgery for partial amputation of a finger earlier this year. Instead of improving in the months following surgery, the pain, which had a stong neuropathic component, became persistent. Further surgery targeting the main nerve in the finger was eventually required to resolve the pain.
I subsequently learned that persistent post-surgical pain represents a major and largely unresolved problem in medicine. It affects large numbers of patients, has important economic consequences, and has a significant effect on quality of life. (2) The significance of surgery as a cause of chronic pain was only first identified in the late 1990s through a large British study of outpatients with chronic pain. It was found that surgery had contributed to persistent pain in 22.5% of the patients.(3, 4) Further studies suggest that persistent pain (ie. lasting longer than 2-3 months) occurs in 10-50% of patients after common surgical procedures. These common procedures include groin hernia repair, breast and thoracic surgery, amputation, knee and hip replacements and coronary artery bypass surgery. (5, 6)
It has been observed that there is often a neuropathic component to CPSP, which makes treatment more challenging. (7) The incidence of CPSP has been found to vary depending on the type of surgery. For example, the incidence of CPSP following thoracic surgery and hysterectomy is about 25%, hip replacement 28% and leg amputation the highest at 59-79%. (8, 9) Severe CPSP accompanied by significant functional impairment is estimated to have an incidence of 5-10%. Thus, with over 45 million surgical procedures performed in the United States each year and over 40 million in the European Union, the number of patients potentially impacted by CPSP each year is significant. (10, 11)
Current pharmacological treatments for CPSP are the same as those commonly prescribed for neuropathic pain caused by post-herpetic neuralgia. These treatments include topical lidocaine patches, **apentin (an anticonvulsant), amitryptiline (an antidepressant) and opioid medications. (9, 12). However, as is the case with neuropathic pain, current treatments have failed to adequately address CPSP, meaning that there is a significant unmet need.
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