“The pathological changes responsible for the symptoms of schizophrenia are essentially unknown. Nevertheless, hypotheses on the roles of particular neurotransmitters abound and it could be stated that the number of such theories grows proportionally to the number of neurotransmitters discovered.”
“Schizophrenia is most likely a multi-neurotransmitter-system disease, caused by a factor or factors that could be acting on any of these systems.”
“In the first completed open (as opposed to blind) study of the compound of the invention in schizophrenic patients, six out of eight patients who completed at least 2 weeks of treatment showed between 66% and 87% improvement at 4 weeks, as assessed on BRPS scale, at daily dosages between 5 and 30 mg. Preliminary results from a further three ongoing clinical trials now appear to confirm this high level of efficacy and at doses lower than or at the low end of the dosage level used in the first study, for example, at 2.5 and 5 mg per day. Moreover, there is a low incidence of only mild and transient elevation of liver enzymes in patients treated with therapeutic doses, and plasma levels of creatinine phosphokinase (CPK) are lower than with flumezapine, indicating a lower adverse effect on muscular tissue. Furthermore, the compound of the invention causes lower elevation of prolactin levels than other currently used neuroleptic drugs and this suggests fewer disturbances of the menstrual cycle, and less gynecomastia and galactorrhea. No alteration of white blood cell count has been observed in clinical studies. In dog toxicity studies with a closely analogous compound, 2-ethyl-10-(4-methyl-1-piperazinyl)-4H-thieno[2,3-b]-[1,5]benzodiazepine, at a dosage of 8 mg/kg, it was observed that four out of eight dogs showed a significant rise in cholesterol levels, whereas the compound of the invention did not show any rise in cholesterol levels. Overall, therefore, in clinical situations, the compound of the invention shows marked superiority, and a better side effects profile than prior known antipsychotic agents, and has a highly advantageous activity level.”
“Where does a wise man hide a leaf? In a forest.”
“Lilly does not dispute that in relation to obviousness a selection from the prior art cannot be merely arbitrary.”
“There is no definitive explanation as to how the transposition of this halogen substitution can result in a profound change in activity. Molecular topography of clozapine and HF-2046, as determined by X-ray crystallography, does not reveal any significant difference. Electron transfer reactions have been often implicated in reversible attachment of biologically active molecules at a receptor site. Such a shift in nuclear substitution, as above, can contribute to the electronic imbalance between the two benzene rings of the asymmetrical tricyclic system.” [51] The authors surmise that, if an electron withdrawing group such as chlorine, can shift the electronic balance of the molecule to advantage, the same effect might be achievable by replacing ring C (the right hand ring as shown above) with a suitable heterocyclic ring i.e. a ring in which carbon is replaced by another atom, such as nitrogen or sulphur. Such a ring would be electron-rich, and thus create or contribute to the electron imbalance in a different way. In particular, the authors propose replacing benzene ring C with a thieno- ring, a five-membered ring with a sulphur hetero-atom: [52] In order to test this theory, a series of individual compounds is recorded as having been synthesised. The compounds selected use a range of values of R 1, R 2 and R. Compound 6 is ethyl olanzapine: in other words a compound identical to olanzapine but with a ethyl rather than a methyl substituent on the thieno- ring. Olanzapine is not included in the list. [53] The compounds recorded as synthesised were tested for neuroleptic activity by their ability to induce hypothermia in mice and by their comparative scores in conditioned avoidance response and catalepsy tests in rats. The objective (in the case of the CAR and CAT tests) is (as mentioned earlier) to find a drug which blocks the conditioned avoidance response at doses that are lower than those required to induce catalepsy. [54] The results were compared with those obtained with known anti-psychotics, clozapine, haloperidol, thioridazine and cis-flupenthixol. [55] From the results, the authors are able to draw certain conclusions about the relationship between structure and activity: (i) as to the substituent R on the piperazine ring, the authors say that higher alkyl substitution (i.e. anything bigger than methyl) leads to a reduction in activity. However, compounds where R is a hydroxyalkyl group such as hydroxyethyl “retain good activity”; (ii) the substitution of ring A with a halogen atom at position 7 on the retained benzene ring enhanced activity; (iii) a short alkyl substitution (methyl, ethyl, iso-propyl) at position 2 on the thiophene ring seems to increase the activity, but compounds with a bulky (tertiary butyl) or long (n-hexane) group showed only minimal activity. [56] The authors conclude the article in the following way: “Unlike the standard neuroleptics tested, clozapine blocks the conditioned avoidance response in rats at doses which are very much lower than those required to produce catalepsy. It is thought that this profile of activity is associated with the relative lack of extrapyramidal side effects produced by this compound in the clinic. A number of compounds in the present series, e.g. 9, 12, 17,29, and 34, have been found to be more potent than clozapine and show a similar, if less marked, separation of activity in these two tests. This profile of activity needs further development of this class of compounds.” “There is no definitive explanation as to how the transposition of this halogen substitution can result in a profound change in activity. Molecular topography of clozapine and HF-2046, as determined by X-ray crystallography, does not reveal any significant difference. Electron transfer reactions have been often implicated in reversible attachment of biologically active molecules at a receptor site. Such a shift in nuclear substitution, as above, can contribute to the electronic imbalance between the two benzene rings of the asymmetrical tricyclic system.” (i) as to the substituent R on the piperazine ring, the authors say that higher alkyl substitution (i.e. anything bigger than methyl) leads to a reduction in activity. However, compounds where R is a hydroxyalkyl group such as hydroxyethyl “retain good activity”; (ii) the substitution of ring A with a halogen atom at position 7 on the retained benzene ring enhanced activity; (iii) a short alkyl substitution (methyl, ethyl, iso-propyl) at position 2 on the thiophene ring seems to increase the activity, but compounds with a bulky (tertiary butyl) or long (n-hexane) group showed only minimal activity. “Unlike the standard neuroleptics tested, clozapine blocks the conditioned avoidance response in rats at doses which are very much lower than those required to produce catalepsy. It is thought that this profile of activity is associated with the relative lack of extrapyramidal side effects produced by this compound in the clinic. A number of compounds in the present series, e.g. 9, 12, 17,29, and 34, have been found to be more potent than clozapine and show a similar, if less marked, separation of activity in these two tests. This profile of activity needs further development of this class of compounds.”
“First, a selection patent to be valid must be based on some substantial advantage to be secured by the use of the selected members ….. . Secondly, the whole of the selected members must possess the advantage in question. Thirdly, the selection must be in respect of a quality of a special character which can fairly be said to be peculiar to the selected group.”