Use of a peptide and an analgesic pharmaceutical agent

The subject of the present invention is the use of an opioid peptide, commonly called biphalin depicted on figure 2 or specific analogues thereof, presented in the figure 1, particularly in as an intravenous drip or injection or implant, in the treatment of strong, chronic pain caused by inflammation including rheumatoid states, or by neuropathies connected with osteoporosis, or post-accident or postsurgical trauma as well as tumours.

The pain signal induced by organ damage or disease is transmitted to the central nervous system (CNS) , where it induces the sensation of pain. The magnitude of the pain stimulus is regulated by the nociceptive and antinociceptive receptors located on neuronal membranes. Endogenous opioid peptides constitute one of the natural factors decreasing the pain signal as a result of activating antinociceptive receptors. These receptors are also activated by the application of analgesic opioid drugs, such as morphine or fentanyl. Unfortunately, the administration of non-peptide analgesics causes a series of adverse reactions, including tolerance and dependency. The application of a peptide analogue of natural opioid peptides, biphalin, makes it possible to decrease tolerance and dependency formation.

Unfortunately, research has shown that opioid peptides have a limited ability to pass through the blood-brain barrier. According to animal research data related in 1989 at the International Narcotic Research Conference 1989 and subsequently described in post-conference material by B. S. Silbert, A.W. Lipkowski, D. B. Carr, S. K. Szyfelbein, P. F. Osgood, in "Peptides as potential nociceptive drugs. ", on pp. 485-488 of ,,Procc. Int. Narc. Res. Conf.'89", R. Quirion ed., published by Alan R. Liss Inc, New .York, 1990, the activity of the opioid peptide presented in Fig. 2 (commonly referred to as biphalin) following intravenous administration is equivalent to that of morphine. Whereas, D. Kosson, I. Maszczynska Bonney, D. B. Carr, E. Mayzner-Zawadzka, A.W. Lipkowski, described this phenomenon in the article entitled Antinociceptive properties of biphalin after intrathecal application in rats: a reevaluation in the Pharmacological Report. Vol. 57, pp. 545-549, 2005, in that bypassing the blood-brain barrier through directly into the subarachnoid space makes it possible for biphaline to exhibit an activity some 1000-fold that of morphine administered the same way. This means that in healthy individuals the blood-brain barrier successfully stops biphalin from penetrating the CNS. The extensive activity of biphalin administered directly into the CNS is the basis of an invention postulating the use of biphalin as a drug for administration using modern local dosage methods, as described in the 2002 patent application

P355470, submitted to the Polish Patent Office by A. W. Lipkowski, D. B. Carr, I. Bonney, D. Kosson, A. Misicka-Kesik, entitled "Application of peptides with analgesic properties directly to the site of their predicted analgesic activity" . Chronic pain is usually related to a pathological state of inflammation caused by various factors, such as rheumatism or gout or post-surgical or post-traumatic neurodegeneration or tumours. One of the effects of such changes in the organism is an alteration of the permeability of biological barriers, including the barriers separating the blood from the CNS, generally referred to as the "brain-blood barrier". These changes were discussed in the review by W. Pan, entitled ,,Permeability of the blood-brain barrier to neurotropic peptides", on pp. 1435-1442, in the book entitled "Handbook of Biologically Active Peptides", A.J. Kastin Ed., Academic Press, Burlingston, 2006.

The goal of the present invention is to produce an analgesic drug which could be used in patients suffering from chronic pain, at lower doses than corresponding morphine doses. Preferentially, effective treatment doses in ill patients should not induce effects in healthy patients. During intravenous administration of biphalin and specific analogues thereof in animal models it was unexpectedly noted that disease changes induce increased permeability of the blood-brain barrier, as evidenced by the increased efficacy of peripherally administered peptide.

Unexpectedly, it was shown that the opioid peptide biphalin and some selected analogues thereof have increased activity during pathological inflammation. Due to this, these peptides are an example of a new type of analgesic which, when applied peripherally, is stronger acting when its activity is necessary during pain accompanying a disease state, which results in the decreased efficiency of the blood-brain barrier, particularly due to inflammation.

Thus, the subject of the present invention is the application of a peptide presented in Figure 1 in the production of an analgesic drug for patients with a weakened blood-brain barrier, wherein the drug production uses a sub-threshold dose.

"Patients with a weakened blood-brain barrier" for the purposes of the present invention are patients suffering disease states, which are known to weaken the blood-brain barrier, meaning an increase in the permeability of the blood-CNS barrier. In particular, these disease states are all disease states accompanied by inflammation. It is commonly known that the blood-brain barrier is weakened in: rheumatoid states, gout, neuropathic and tumour-induced pain. In a preferential embodiment of the present invention, the pain fought can be induced by a tumour, rheumatoid inflammation, gout, multiple sclerosis, osteoporosis, postsurgical or post-accidental trauma and oncogenic changes. A ,,sub-threshold dose" for the purposes of the present

invention is a dose showing no analgesic activity in healthy persons, meaning persons in whom the blood-brain barrier shows no increased permeability. Because the sub-threshold dose will be different for different species of mammals and patients in various disease states, and will also depend on the method of administration into the bloodstream, it should thus be assumed on a per case basis, that the sub-threshold dose is a dose lower than the lowest effective dose of identically administered morphine capable of eliciting an analgesic effect in said patient. In humans, the minimum effective dose usually used as an initial analgesic dose is 1 mg, as found in literature. Thus, in particular embodiments of the present invention, the sub-threshold dose in humans will be a dose less than 1 mg, preferentially less than 0.1 mg, preferentially less than 0,01 mg, and particularly preferentially, in patients with considerable disease-induced blood-brain-barrier permeability the dose will be less than 10 ^~3 mg.

The method of administration can be any known method of administration used for morphine. In particular, intravenous administration may be used, particularly as a drip; intraperitoneal or subdermal administration, preferentially as a subdermal intraperitoneal implant.

Also, the preparation administered may be in the form of various formulations. The peptide can be administered as the only active substance, or may be a component of a multi-drug

pharmaceutical composition used in therapy. In particular, the peptide used according to present invention can be in the form of a sterile lyophilisate, which is to be dissolved in a certain quantity of physiological saline prior to administration. It may also be used as a ready-to-use solution.

The present invention reveals the use of the opioid peptide with the formula shown in Figure 1 as an effective analgesic, preferentially following peripheral administration, during disease states which also result in increased blood-brain barrier permeability.

To better illustrate the present invention based on analgesic activity following the peripheral administration of the opioid peptide known as biphalin or its analogues during inflammation inducing changes in blood-CNS barrier permeability including, rheumatoid states, or oncogenic or neuropathic pain, the effects are shown in examples of activity in animal pain research models. However, the scope of present invention should not only be limited to the examples given below.

The similar results and activities shall be obtained for all selected peptides disclosed in the application.

Example I. Inflammation was induced in mice through the administration of Freund' s adjuvant into a limb. After two days, a progressing inflammation was observed. The analgesic

activity of biphalin was observed following a week, during acute pain caused by tail dipping in water at a temperature of 55°C. The intravenous administration of biphalin at 50 μg/kg caused a complete disappearance of the pain reaction in mice with inflammation. In the control group, which lacked the inflammation, no effect was observed for the same dose, administered identically.

Example II. In an animal pain model of tumour metastasis, inflammation was induced though the injection of a million human ovarian cancer cells into a rear limb. After two days, we observed a progressing inflammation induced by tumour take. The analgesic activity of biphaline was observed after two weeks, during acute pain caused by tail dipping in water at a temperature of 55°C. The intraperitoneal administration of the opioid peptide biphalin at 100 μg/kg caused a complete disappearance of the pain reaction in mice with inflammation. In the control group, which lacked the inflammation, a similar analgesic effect necessitated the use of a dose of 1 mg/kg.

Example III. In an animal pain model of tumour metastasis, inflammation was induced though the injection of a million human ovarian cancer cells into a rear limb. After two days, we observed a progressing inflammation induced by tumour take. The analgesic activity of (Tyr-Ser-Gly-Phe-NH-) ₂ was observed after two weeks, during acute pain caused by tail

dipping in water at a temperature of 55°C. The intraperitoneal administration of the opioid peptide (Tyr- Ser-Gly-Phe-NH-)2 at 50 μg/kg caused a complete disappearance of the pain reaction in mice with inflammation. In the control group, which lacked the inflammation, a similar analgesic effect necessitated the use of a dose of 4 mg/kg.

Example IV. In an animal rheumatoid inflammation model, an anaesthetised rat was injected with homogenates of thermically inactivated Mycobacterium butyricum suspended in sunflower oil at a volume ratio of 1:1 into the tarsal joint. After two weeks inflammation was observed. The analgesic effect on acute pain was observed using thermal stimulation of the tail. Biphalin administered at 0.5 mg/kg completely blocked pain effects. In the control group given the same amount of biphalin, no antinociceptive effects were observed.

Example V. In an animal rheumatoid inflammation model, an anaesthetised rat was injected , with homogenates of thermically inactivated Mycobacterium butyricum suspended in sunflower oil at a volume ratio of 1:1 into the tarsal joint. After two weeks inflammation was observed. The analgesic effect on acute pain was observed using thermal stimulation of the tail. (Tyr-D-Thr-Gly-Trp-NH-) ₂ administered at 0.5 mg/kg completely blocked pain effects. In the control group given the same amount of , (Tyr-D-Thr-Gly-Trp-NH-) ₂ no

antinociceptive effects were observed after administration of 4 mg/kg.