Drug development history, "overview," and what are GCPs?

History shows that regulation of the pharmaceutical industry came about as a result of unfortunate incidences in which self-control by the industry was insufficient. All facets of drug manufacturing and preclinical laboratory research and development are regulated by GMPs and GLPs. Only part of the GCPs, as proposed, have become regulations. The pharmaceutical industry has an attrition rate of NCEs, from discovery to product, of 10,000 : 2. Research and development to market a product consumes 12 years (approximately 71% of patent life) and costs more than +250 million. The industry will be well served to closely monitor itself through conformance to GCP guidelines and regulations to avoid further government regulation.

Differential blocking effects of prazosin and yohimbine on vasopressor responses to sympathetic nerve stimulation and intravenous norepinephrine in the pithed rat.

The effects of prazosin and yohimbine on the vasopressor response to sympathetic nerve stimulation, and to i.v. administration of norepinephrine were studied in the pithed rat to ascertain whether prazosin and yohimbine would preferentially block pressure responses due to exogenous versus endogenous alpha-adrenergic receptor activation. Prazosin (3 and 10 micrograms/kg, i.v.) was more effective in blocking the response due to sympathetic nerve stimulation than that due to i.v. norepinephrine. On the other hand, yohimbine (0.3 and 1 mg/kg, i.v.) produced greater inhibition of the i.v. norepinephrine response than the sympathetic nerve stimulation response. Yohimbine at the 0.1 mg/kg dose enhanced the nerve stimulation response while at higher doses the response was either unchanged (at 0.3 mg/kg) or substantially reduced (at 1 mg/kg). In this model, prazosin and yohimbine showed dose-related blocking effects on the pressor response of phenylephrine and clonidine, respectively. The results suggest that prazosin and yohimbine preferentially block the pressor responses of postsynaptic alpha-adrenergic receptor activation due to endogenous and exogenous norepinephrine, respectively. The diverse effects of yohimbine on the sympathetic nerve stimulation response may be due to an action on both the presynaptic (low dose) and postsynaptic (high dose) alpha-2 adrenergic receptors in vascular smooth muscle.

Effect of structural change on acute toxicity and antiinflammatory activity in a series of imidazothiazoles and thiazolobenzimidazoles.

The effect of structural change on the biological activity of a series of imidazothiazoles and thiazolobenzimidazoles is described. It was found that compounds with polar substituents at the 2 or 3 position of the ring system are less acutely toxic while maintaining antiinflammatory activity. Other structural changes, such as the incorporation of a gem-dimethyl substituent in the 6 position, increase acute toxicity and eliminate antiinflammatory activity. The compound with the best activity/toxicity ratio contains an alkyl sulfonyl substituent on the thiazole ring. The thiazolobenzimidazole analogues are more potent than the imidazole analogues.

Antihypertensive 5,6-diarylpyridazin-3-ones.

The synthesis of a series of 5,6-diarylpyridazinones is described. Some members of this series display an antihypertensive effect in both the spontaneously hypertensive rat (SHR) model and the deoxycorticosteroid (DOCA) model of hypertension. The most potent compounds in the series have halogen substituents on the 5,6-diphenyl rings, a beta-substituted alkyl group at the 2 position of the ring, and acetyl or cyano substituent at the 4 position.

Lipophilic and hydrophilic esters of 4-acetyl-2-(2-hydroxyethyl)-5,6-bis(4-chlorophenyl)-2H-pyridazin-3-one as antihypertensive agents.

In an attempt to enhance the antihypertensive activity of 4-acetyl-2-(2-hydroxyethyl)-5,6-bis(4-chlorophenyl)-2H-pyridazin-3-one, 1, a series of lipophilic and hydrophilic esters was synthesized. These derivatives possessed increased lipid and aqueous solubility, respectively. The esters, in general, cause a larger blood-pressure drop than 1 when tested at high doses in the spontaneously hypertensive rat (SHR) model. At lower doses the antihypertensive activity is the same as with 1.

Synthesis and anti-inflammatory evaluation of 3-methylthio-1,2,4-triazines, 3-alkoxy-1,2,4-triazines, and 3-aryloxy-1,2,4-triazines.

To develop nonacidic, nonsteroidal anti-inflammatory agents without GI complications, a series of asymmetric triazines was synthesized and evaluated for anti-inflammatory efficacy in the carrageenan-induced pedal edema assay. Toxicity was estimated by determination of approximate LD50 values in mice. Twenty-five compounds possessed activity comparable to the standard, indomethacin. Thirteen of the 25 compounds were selected for dose-response evaluation in the carrageenan assay based on their relative toxicity and anti-inflammatory activity. Neurotoxicity of the 13 triazines was estimated by determination of NTD50 values in mice. Five of the 13 compounds tested in the dose-response assay were active in terms of anti-inflammatory efficacy (ED50 values) and lack of overt neurotoxicity (NTD50 values) when compared to indomethacin. To determine the effect of these five developmental triazines on chronic inflammation, they were evaluated in the adjuvant-induced polyarthritis assay. One was comparable to indomethacin in reducing adjuvant-induced inflammation in this assay.

Synthesis and antihypertensive activity of novel 3-hydrazino-5-phenyl-1,2,4-triazines.

In an effort to develop antihypertensive agents with peripheral vasodilator activity, a series of 40 novel 3-hydrazino-5-phenyl-1,2,4-triazines (II) were synthesized and evaluated in the spontaneously hypertensive rat assay (SHR assay). Based on the performance of the structurally related standard, hydralazine (I), 15 triazines were active. Thirteen of these hypotensive triazines possessed LD50 values in the mouse greater than I (LD50 = 100 mg/kg); only one active triazine had an LD50 value greater than 300 mg/kg (11d). Four asymmetric triazines had moderate antihypertensive activity and LD50 values greater than 300 mg/kg (6b, 7c, 8f, and 9g). Based on the relationship between toxicity and antihypertensive activity, three triazines (8f, 9g, and 11d) were chosen for dose-responses studies in the SHR assay. None were as efficacious as I, but all three were less toxic, resulting in similar therapeutic indices relative to I.

The absence of sensitivity changes of the rabbit oviduct to phenylephrine and isoproterenol during early gestation.

The response of the rabbit perfused oviduct in vivo to phenylephrine (PE), isoproterenol (ISO) and epinephrine (EPI) was studied to determine if a purported change from alpha-adrenergic receptor dominance to beta-adrenergic receptor dominance during early gestation occurs (i.e. prior to implantation). The response of the tissue to PE did not change during early gestation, even in the presence of beta-receptor blockade by propranolol. The response to ISO of the PE-stimulated oviduct also did not change. However, the dose-response curve to EPI was shifted horizontally to the right 4 days after mating suggesting a tissue desensitization. It was concluded that the decreased oviductal sensitivity to EPI observed during early gestation could not be attributed to a change from alpha-receptor dominance to beta-receptor dominance.

The effects of propranolol HCl in hippocampal-lesioned rats.

Experiments were conducted to determine the effects of propranolol administration in rats lesioned in the hippocampal area. Chronic oral administration of propranolol to intact rats produced a significant decrease in mean systolic blood pressure. No significant changes in blood pressure were produced with propranolol treatment in rats lesioned in the septal or anterior hypothalamic areas, whereas, in rats lesioned in the hippocampal area, a significant elevation of blood pressure was observed. These findings confirm previous results that suggest that the hypotensive effects observed with chronic propranolol administration are mediated via the hippocampus.

Cardiovascular effects of 5-hydroxypropranolol (ORF 12592) in dogs.

ORF 12592, the 5-hydroxy analog of propranolol, produced reductions in mean arterial pressure, heart rate, cardiac contractility and hind limb perfusion pressure in the anesthetized normotensive dog. Blood pressure and heart rate were also lowered in the carotid-sinus denervated dog. ORF 12592 blocked heart rate and blood pressure responses induced by isoproterenol. Similar results were observed with propranolol administration except for a transient decrease in blood pressure in the mormotensive dog. These results indicate that ORF 12592 possesses antihypertensive and beta-blocking properties in the anesthetized dog.

A characterization of the effects of acetylcholine on the rabbit oviduct.

The effect of acetylcholine (ACh) on the perfused oviduct of the rabbit was investigated. The response of the oviduct to ACh during early gestation was variable, i.e., biphasic (contraction followed by slight relaxation) greater than contractile greater than relaxation. The responsiveness of the oviduct to the contractile effect decreased progressively during early gestation, similar to that previously reported for norepinephrine (NE). The contraction produced by ACh was antagonized by chlorisondamine and atropine and also by phentolamine and pretreatment with reserpine. It was concluded that the response produced by ACh may be mediated in part through the release of NE.

Antihypertensive activity of a propranolol analog (ORF 12,592) in rodents.

Studies were carried out to determine the antihypertensive effects of the 5-hydroxy derivative (ORF 12,592) of propranolol. Acute administration of ORF 12,592 produced a reduction in mean systolic blood pressure in desoxycorticosterone acetate (DOCA) rats and in spontaneously hypertensive rats (SHR). Propranolol was not effective in DOCA rats and produced a significant blood pressure reduction in SHR 48 hr after acute administration. These results demonstrated antihypertensive activity of an analog of propranolol and support the concept that the antihypertensive effects of propranolol may be mediated through a metabolite.

Dose-response effects of prostaglandin F2alpha on the rabbit oviduct: reproductive endocrine influence and tachyphylaxis.

The dose-response effect of PGF2alpha on the perfused oviduct of estrous and ovariectomized rabbits was determined. The oviducts of ovariectomized rabbits were more sensitive to the contractile effects of PGF2alpha than those of estrous rabbits. This was demonstrated by a significant difference in the slope of the dose-response curves and in the magnitude of the maximum responses between the two groups. Blood pressure responses (depressor) to PGF2alpha were not affected by the reproductive hormonal status of the rabbits. The oviduct (estrous rabbits) developed tachyphylaxis to the effect of PGF2alpha. It was concluded that the response of the rabbit oviduct to PGF2alpha is dependent on the reproductive hormone status of the animal and that the oviduct becomes insensitive to the effects of PGF2alpha with repeated administration.

A dose-response comparison of PGA2, PGE1 and PGE2 using the phenylephrine-stimulated perfused oviduct of the rabbit.

The phenylephrine-stimulated perfused oviduct of the rabbit was evaluated as a model for studying the activity of prostaglandins that produce inhibition of the oviducal smooth muscle. Elevation of the normal "tone" of the oviduct by perfusing phenylephrine through the lumen permitted quantitation of the responses to PGA2, PGE1 and PGE2 by measuring the magnitude of the inhibitory response produced by the agents. PGE2 was relatively more potent, efficacious and specific for the oviduct than PGA2 or PGE1. It was concluded that the model was suitable for comparative dose-response studies of PGA2, PGE1 and PGE2 and their analogs.

Resistance of androgen-mediated aggressive behavior in mice to flutamide, an antiandrogen.

Flutamide (FTA), an anti-androgenic compound, inhibited the effects of methyltestosterone (MT) on the weight of the ventral prostate, seminal vesicles and levator ani in male castrate mice. Castration prevented the development of aggressive behavior in mice isolated for 3 weeks. While chronic administration of MT to castrate isolated mice returned the incidence of fighting behavior to control values, chronic administration of FTA + MTdid not significantly reduce the incidence of fighting as compared to castrate + MT values. These results suggest that the mechanism for androgen stimulation of secondary sex organ weight may differ from that involved in the development and maintenance of aggression resulting from isolation.

Changes in the sensitivity of adrenergic receptors in the oviduct during early gestation in the rabbit.

There is evidence to indicate that the transport of an egg through the rabbit oviduct is controlled through an interaction of the sympathetic nervous system and ovarian hormones. The effect of norepinephrine (NE) on the contractility of the oviduct during the first 8 days of gestation was studied using the rabbit perfused oviduct. The sensitivity of the alpha-adrenergic receptors of the oviduct to NE decreased progressively during early gestation. This was reflected in a potency change and a decrease in the maximal response obtained. These data support the concept that an isthmic sphinctering effect mediated by the autonomic nervous system may play a role in the regulation of egg transport through the oviduct. Blood pressure responses to NE did not change during early pregnancy except that the responses to NE were significantly enhanced immediately after mating. This suggests that the sensitivity changes to autonomic agents during early gestation may be selective for reproductive tissues.

PIP: The effect of norepinephrine (NE) on the contractility of the perfused oviduct was studied during the 1st 8 days of gestation in the rabbit. During early gestation, the sensitivity of the alpha-adrenergic receptors of the oviduct progressively decreased, the change being reflected by a change in potency and a decrease in the maximal response. Carotid artery blood pressure was significantly increased immediately after mating (p less than .05), though the responses returned to normal during early pregnancy. The results support the hypothesis that the regulation of egg transport through the oviduct may be influenced by an isthmic sphinctering effect mediated by the autonomic nervous system. It is suggested that the response changes to autonomic agents during early pregnancy may be selective for reproductive tissue.

An evaluation of the hot plate technique to study narcotic antagonists.

The mouse hot plate model, with slight differences from the way it is used to study narcotic analgesics, was evaluated as a method for determining the oral effectiveness, relative potency and duration of action of two standard narcotic antagonists, naloxone and naltrexone, and a new agent, 6-desoxy-6-methylene-naltrexone (ORF 11676). Naltrexone and ORF 11676 were found to be more effective orally than naloxone. Naltrexone and ORF 11676 were equipotent by 3 routes of administration and both were more potent than naloxone. Naloxone produced a significantly shorter duration of action than the other two drugs. It was concluded that the mouse hot plate method, used to detect and characterize the activity of narcotic antagonists, provides information compatible with that obtained in other species, including man.