Steric structure-activity relationship of cyproheptadine derivatives as inhibitors of histone methyltransferase Set7/9

Set7/9 is a histone lysine methyltransferase, but it is also thought to be involved in a wide variety of pathophysiological functions. We previously identified cyproheptadine, which has a characteristic butterfly-like molecular conformation with bent tricyclic dibenzosuberene and chair-form N-methylpiperidine moieties, as a Set7/9 inhibitor. In this work, we synthesized several derivatives in order to examine the steric structure-inhibitory activity relationship. We found that even a small change of molecular shape due to reduction or replacement of the 10,11-olefinic bond of the tricyclic ring generally resulted in a drastic decrease of the inhibitory activity. Our results should be useful not only for development of more potent and selective inhibitors, but also for the construction of novel inhibitor scaffolds.

FT-IR and FT-Raman spectra, molecular structure and first-order molecular hyperpolarizabilities of a potential antihistaminic drug, cyproheptadine HCl

Cyproheptadine hydrochloride (CYP HCl) {4-(5H-dibenzo[a,d]-cyclohepten-5-ylidene)-1-methylpiperidine hydrochloride} is a first-generation antihistamine with additional anticholinergic, antiserotonergic, and local-anesthetic properties. The geometry optimization, Mulliken atomic charges and wavenumber and intensity of the vibrational bands of all of the possible modes of CYP HCl have been calculated using ab initio Hartree-Fock (HF) and density functional theory (DFT) employing the B3LYP functional with the 6-311G(d,p) basis set. We have compared the calculated IR and Raman wavenumbers with experimental data. Quantum-chemical calculations of the geometrical structure, energies, and molecular electrostatic potential and NBO analysis of CYP HCl have been performed using the B3LYP/6-311G(d,p) method. The electric dipole moment (μ), static polarizability (α) and the first hyperpolarizability (β) values of the title compound have been computed using HF and DFT methods. The study reveals that the antihistaminic pharmacological property of CYP HCl has a large β value and, hence, may in general have potential applications in the development of non-linear optical materials. The experimental and calculated results for CYP HCl have also been compared with those for mianserin HCl.

Rupatadine in allergic rhinitis and chronic urticaria

Histamine is the primary mediator involved the pathophysiology of allergic rhinitis and chronic urticaria, and this explains the prominent role that histamine H(1)-receptor antagonists have in the treatment of these disorders. However, histamine is clearly not the only mediator involved in the inflammatory cascade. There is an emerging view that drugs which can inhibit a broader range of inflammatory processes may prove to be more effective in providing symptomatic relief in both allergic rhinitis and chronic urticaria. This is an important consideration of the Allergic Rhinitis and its Impact on Asthma (ARIA) initiative which provides a scientific basis for defining what are the desirable properties of an 'ideal' antihistamine. In this review of rupatadine, a newer dual inhibitor of histamine H(1)- and PAF-receptors, we evaluate the evidence for a mechanism of action which includes anti-inflammatory effects in addition to a powerful inhibition of H(1)- and PAF-receptors. We assess this in relation to the clinical efficacy (particularly the speed of onset of action) and safety of rupatadine, and importantly its longer term utility in everyday life. In clinical trials, rupatadine has been shown to be an effective and well-tolerated treatment for allergic rhinitis and chronic idiopathic urticaria (CIU). It has a fast onset of action, producing rapid symptomatic relief, and it also has an extended duration of clinical activity which allows once-daily administration. In comparative clinical trials rupatadine was shown to be at least as effective as drugs such as loratadine, cetirizine, desloratadine and ebastine in reducing allergic symptoms in adult/adolescent patients with seasonal, perennial or persistent allergic rhinitis. Importantly, rupatadine demonstrated no adverse cardiovascular effects in preclinical or extensive clinical testing, nor negative significant effects on cognition or psychomotor performance (including a practical driving study). It improved the overall well-being of patients with allergic rhinitis or CIU based on findings from quality of life questionnaires and patient global rating scores in clinical trials. Thus, rupatadine is a recently introduced dual inhibitor of histamine H(1)- and PAF-receptors, which has been shown to be an effective and generally well-tolerated treatment for allergic rhinitis and chronic urticaria. It possesses a broader profile of anti-inflammatory properties inhibiting both inflammatory cells and a range of mediators involved in the early- and late-phase inflammatory response, but the clinical relevance of these effects remain to be clarified.

Similarity in drugs: reflections on analogue design

A survey of novel small-molecule therapeutics reveals that the majority of them result from analogue design and that their market value represents two-thirds of all small-molecule sales. In natural science, the term analogue, derived from the Latin and Greek analogia, has always been used to describe structural and functional similarity. Extended to drugs, this definition implies that the analogue of an existing drug molecule shares structural and pharmacological similarities with the original compound. Formally, this definition allows the establishment of three categories of drug analogues: analogues possessing chemical and pharmacological similarities (direct analogues); analogues possessing structural similarities only (structural analogues); and chemically different compounds displaying similar pharmacological properties (functional analogues).

Discovery, structure–activity relationship study, and oral analgesic efficacy of cyproheptadine derivatives possessing N-type calcium channel inhibitory activity

Antiallergic drug cyproheptadine (Cyp) is known to have inhibitory activities for L-type calcium channels in addition to histamine and serotonin receptors. Since we found that Cyp had an inhibitory activity against N-type calcium channel, Cyp was optimized to obtain more selective N-type calcium channel blocker with analgesic action. As a consequence of the optimization, we found 13 with potent N-type calcium channel inhibitory activity which had lower inhibitory activities against L-type calcium channel, histamine (H1), and serotonin (5-HT2A) receptors than those of Cyp. 13 showed an oral analgesic activity in rat formalin-induced pain model.

Lethal, oedema, haemorrhagic activity of spotted butterfish (Scatophagus argus, Linn) sting extract and its neutralization by antiserum and pharmacological antagonists

An attempt has been made in this communication to develop antiserum in rabbit against Scatophagus. argus sting extract. Antiserum did not neutralized the sting extract induced proinflammatory and haemorrhagic activity but successfully neutralized lethality upto 2LD50. Cyproheptadine, indomethacin and BW 755C pretreatment significantly reduced sting extract induced proinflammatory activity. The haemorrhagic activity of sting extract was significantly inhibited by temperature, UV-exposure, EDTA, cyproheptadine, indomethacin and BW 755C pretreatment. The results conclude that the local effects of S.argus venom is likely to be mediated through release of mediators and may be encountered by pharmacological antagonists better than the antiserum.

The histamine H1-receptor antagonist binding site. Part I: Active conformation of cyproheptadine

The active conformation of several histamine H1-antagonists is investigated. As a template molecule we used the antagonist cyproheptadine, which consists of a piperidylene ring connected to a tricyclic system. The piperidylene moiety is shown to be flexible. The global minimum is a chair conformation but, additionally, a second chair and various boat conformations have to be considered, as their energies are less than 5 kcal/mol above the energy of the global minimum. Two semi-rigid histamine H1-antagonists, phenindamine and triprolidine, were fitted onto the various conformations of cyproheptadine in order to derive the pharmacologically active conformation of cyproheptadine. At the same time, the active conformation of both phenindamine and triprolidine was derived. It is demonstrated that, within the receptor-bound conformation of cyproheptadine, the piperidylene ring most probably exists in a boat form.