FDA designations for therapeutics and their impact on drug development and regulatory review outcomes.

New prescription drugs receive approval from the US Food and Drug Administration (FDA) based on tests establishing safety and adequate and well-controlled trials demonstrating "substantial evidence" of efficacy. However, a number of legislative and regulatory initiatives, the most recent being the breakthrough therapy designation created in 2012, give the FDA flexibility to approve drugs on the basis of less rigorous data in situations of greater clinical need. These expedited development and review pathways now contribute to a majority of all new drug approvals and have important benefits in encouraging efficient availability of transformative drugs. They also have a number of risks, including a heightened possibility that the drugs will be discovered to be ineffective or unsafe after widespread use, and confusion by patients and physicians over what it means for a product to be "FDA approved."

Privileged structures: applications in drug discovery.

Over the past 15 years the privileged structure concept has emerged as a fruitful approach to the discovery of novel biologically active molecules. Privileged structures are molecular scaffolds with versatile binding properties, such that a single scaffold is able to provide potent and selective ligands for a range of different biological targets through modification of functional groups. In addition, privileged structures typically exhibit good drug-like properties, which in turn leads to more drug-like compound libraries and leads. The net result is the production of high quality leads that provide a solid foundation for further development. The identification of privileged structures will be discussed, emphasizing the importance of understanding the structure-target relationships that confer "privileged" status. This understanding allows privileged structure based libraries to be targeted at distinct target families (e.g. GPCRs, LGIC, enzymes/kinases). Privileged structures have been successfully exploited across and within different target families and promises to be an effective approach to the discovery and optimization of novel bioactive molecules. The application of the privileged structure approach, both in traditional medicinal chemistry and in the design of focused libraries, will be discussed with the aid of illustrative examples.

Free running circadian rhythms of melatonin, luteinizing hormone, and cortisol in Syrian hamsters bearing the circadian tau mutation.

The tau mutation of Syrian hamsters induces a robust reduction in the period of circadian activity rhythms, from 24 h (wild-type; tau++) to 22 h (heterozygote; tauS+) and 20 h (homozygous mutant, tauSS). Here, we examine the effect of this mutation on circadian rhythms of LH, melatonin, and cortisol in ovariectomized hamsters. Free running circadian rhythms were observed in all three hormones. In each genotype, endocrine rhythms were synchronized with concurrently assessed activity rhythms, suggesting a shared period around 20 h in tauSS, 22 h in tausS+, and 24 h in tau++. Phasing with respect to the activity rhythm was generally similar in tau++ and mutant genotypes. However, melatonin concentrations rose significantly earlier in tauSS than in tau++ animals. Explanted pineals from both genotypes exhibited a similar time course of response to norepinephrine administration, suggesting that the phase advance of melatonin production observed in tauSS in vivo is not a direct effect of the tau mutation within the pinealocyte. The demonstration of reduced period endocrine rhythms in the mutant genotypes extends previous behavioral studies and, together with recent work on rhythmicity in the isolated retina, suggests an ubiquitous influence of the tau mutation on the processes of circadian rhythm generation in this species.

Structurally similar small molecule photoaffinity CCK-A agonists and antagonists as novel tools for directly probing 7TM receptors-ligand interactions.

Incorporation of photolabile benzoyl (2a-d) or trifluoromethyl-3H-diazirine (3a-d) substituents into 1,5-benzodiazepine ligands did not significantly impair the rat CCK-A binding affinity of either agonists or antagonists. The modified agonist ligands also retained functional potency and efficacy in the rat amylase assay. Despite their strong structural similarity, the SAR of this limited set of compounds suggests that these small molecule antagonists and agonists might differ in their mode of binding to the CCK-A receptor. Preliminary affinity results show that representative agonists and antagonists from these series can be used to efficiently covalently label the CCK-A receptor.

A cyclic phosphonamidate analogue of glucose as a selective inhibitor of inverting glycosidases.

Recent work in the synthesis of cyclic phosphonate analogues of glucose [Darrow, J.W.; Drueckhammer, D.G. (1994) J. Org. Chem. 1994, 59, 2976] has been extended to the synthesis of a corresponding phosphonamidate analogue. A phosphonate salt, phosphonate methyl ester, and phosphonamidate analogue were tested as inhibitors of two inverting alpha-glycosidases, (trehalase and glucoamylase), and two retaining glycosidases, (alpha-glucosidase and beta-glucosidase). No inhibition of any of these enzymes was observed with the phosphonate salt or methyl ester. However, the phosphonamidate gave moderate competitive inhibition of the two inverting glycosidases and the retaining alpha-glucosidase but no inhibition of beta-glucosidase. The phosphonamidate showed enhanced binding relative to a simple monosaccharide only with the inverting glycosidases. This enhanced binding is believed to be due to hydrogen bonding interactions between the phosphonamidate group and two active site carboxylate residues implicated in catalysis. The selectivity toward inverting glycosidases is consistent with differences in distance of an active site carboxylate from the anomeric carbon of the glycoside substrate for the inverting versus the retaining glycosidases.

Regulation of rat luteinizing hormone beta gene expression in transgenic mice by steroids and a gonadotropin-releasing hormone antagonist.

Transcriptional regulation of the rat LH beta (rLH beta) gene was studied through the use of transgenic mice bearing a region of the rLH beta gene (from -2 kb to +41 bp) linked to a luciferase (LUC) reporter gene. All 7 founder mice were successfully bred with B6SJLF1 mates and exhibited germ line transmission of the LH beta LUC transgene. Levels of rLH beta LUC activity were highest in the pituitary, but activity was also detected in ovary, testis, and hypothalamus. Pituitary rLH beta LUC activity was found to be regulated by gender, gonadectomy, gonadal steroid replacement, and GnRH antagonist administration. Females had higher basal pituitary rLH beta LUC activity than males. This activity was increased 2- to 4-fold seven days postovariectomy, and stimulated activity was suppressed to intact levels by daily injections of 17 beta estradiol (E2; 300 ng). In males, castration increased pituitary LUC activity 2- to 4-fold, and this suppressed to intact levels by daily injections of 25 micrograms dihydrotestosterone (DHT). The postgonadectomy rise in pituitary rLH beta LUC activity in females and males was blocked by daily administration of the GnRH antagonist Antide (60 micrograms), which also suppressed serum LH and LH beta mRNA levels to a similar extent. Rat LH beta LUC activity measured in the hypothalamus was not altered by gonadectomy or gonadal steroid or Antide treatment, demonstrating that this regulation is pituitary-specific. These results indicate that feedback regulation of pituitary rLH beta LUC gene expression is operational in this transgenic mouse model.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of photoperiod and gonadal steroids on hibernation in the European hamster.

Torpor was monitored daily in adult male and female European hamsters (Cricetus cricetus) induced to hibernate by exposure to a cold environment (6 degrees C). The effect of photoperiodic manipulations or administration of exogenous gonadal steroids was examined in gonadectomized or intact hamsters. 1. Gonadal regression occurred in all short day, but only in some long day, cold-exposed hamsters. Entry into hibernation was not observed until reproductive regression had occurred. Thus, gonadal atrophy appears to be a necessary precondition for hibernation. 2. Castrated hamsters in the short day cold condition showed a significantly greater incidence of torpor than those in the long day cold condition. Hence, photoperiod affected torpor independently of its effect on the gonadal cycle. 3. Testosterone, when administered via silastic capsules at near physiological levels, completely inhibited torpor in gonadectomized male and female hamsters hibernating in the short day cold condition. 4. In ovariectomized females, torpor was unaffected by progesterone treatment, but partially inhibited by estradiol. A greater inhibition of torpor was observed when estradiol-primed females were administered both estradiol and progesterone simultaneously. Thus, the effect of both hormones may be functionally comparable to that of the single testicular hormone. 5. Estradiol inhibited torpor to a greater extent in intact and ovariectomized female hamsters hibernating in long days than those in short days, suggesting an effect of photoperiod on responsiveness to estradiol. These results indicate an inverse relationship between the gonadal and hibernation cycles, and a probable role for gonadal steroids to influence the timing of the hibernation season. However, non-gonadal factors must also be involved in controlling hibernation, since photoperiod affected the incidence of torpor in gonadectomized animals and because hamsters were able to terminate hibernation in the absence of gonadal hormones.

Uterine steroid hormone receptors during the estrous cycle and during hibernation in the Turkish hamster (Mesocricetus brandti).

The Turkish hamster is a long-day breeder that hibernates for 4-5 mo if exposed to a short-day, cold environment. The objective of this study was to assess the uterine responsiveness of the hibernating animal to ovarian steroids. Our approach was 1) to characterize and determine uterine estrogen (E) and progesterone (P) receptors (R) during hibernation as compared to the levels observed in cycling females that had terminated hibernation, and 2) to assess the responsiveness of the uterus to E during hibernation by its ability to induce uterine P receptor. Females were exposed to short days (10L:14D) for 2 mo and then were placed in a cold-room (10L: 14D, 6 +/- 1 degrees C). After 2 or 4 mo in the cold, hibernating animals were killed and uterine steroid receptors were determined by 3H-steroid binding assay. Uterine receptors were also determined in cycling Turkish hamsters on each morning of the estrous cycle. Values for uterine receptors (pmol/g tissue, n = 4-6) during the estrous cycle (estrus, diestrus I, diestrus II, proestrus) were: 4.3 +/- 0.78, 3.9 +/- 0.19, 4.1 +/- 0.25, 3.7 +/- 0.5 for cytosolic ER; 36.6 +/- 5.8, 32.2 +/- 6.8, 36.3 +/- 1.5, 54.4 +/- 1.9 for cytosolic PR; 0.59 +/- 0.11, 0.54 +/- 0.07, 1.06 +/- 0.05, 1.42 +/- 0.17 for nuclear ER. Hibernating (torpid) animals sampled after 2 mo in the cold showed a significant (p less than 0.05) depression of cytosolic ER (2.6 +/- 0.12, n = 5) and cytosolic PR (19.0 +/- 2.6, n = 8) as compared to any day of the estrous cycle.(ABSTRACT TRUNCATED AT 250 WORDS)

Patterns of reproductive hormone secretion in hibernating Turkish hamsters.

Changes in gonadal state and in circulating reproductive hormones [follicle-stimulating hormone (FSH), prolactin (PRL), and testosterone] were studied for 30 wk in male Turkish hamsters (Mesocricetus brandti) induced to hibernate by exposure to a short-day, cold environment [10:14-h light-dark (LD) cycle, 6 +/- 1 degree C]. Similar measures were compared in hamsters maintained under short-day warm conditions (10:14-h LD, 21 +/- 2 degrees C). A decrease in testicular size and in hormone levels was observed after 9-12 wk of short-day exposure in all animals. After 24 wk, hormone levels rose again, accompanied by testicular recrudescence, in short-day warm hamsters and in hamsters that failed to hibernate in the cold. For animals that hibernated the temporal pattern of endocrine and gonadal changes differed only slightly in comparison. Testicular recrudescence of hibernators lagged approximately 3 wk behind that of short-day warm hamsters. Hormone levels were generally lower in hibernators sampled during bouts of torpor than during bouts of spontaneous arousal from torpor. A marked elevation of serum FSH was observed in aroused hibernators well before the end of the hibernation season (at 21 wk of short-day exposure). Mean testosterone and PRL values had increased by wk 27, after hibernation was terminated in the majority of animals. These results indicate that testosterone may not be essential for the termination of the hibernation season. The data also suggest that an endogenous timing mechanism, resistant to the decreased body temperature experienced during torpor, may function to trigger a resurgence of the neuroendocrine-gonadal axis at the end of the winter season.

Effects of photoperiod on hibernation in castrated Turkish hamsters.

Hibernation and circulating reproductive hormones [luteinizing hormone, follicle-stimulating hormone, and prolactin (LH, FSH, and PRL)] were studied for greater than 40 wk in castrated male Turkish hamsters (Mesocricetus brandti) housed in either a long-day cold or short-day cold environment. A significantly greater percentage of short-day animals hibernated than did long-day animals, indicating that short-day exposure can predispose Turkish hamsters to enter hibernation and that this photoperiodic effect cannot be explained entirely by the inhibitory influence of short days on testicular endocrine activity. Long-day castrates showed no significant changes in LH or FSH levels during the experiment. In the short-day castrates serum LH, FSH, and PRL levels were reduced after 4-9 wk and increased again after 18-23 wk of short-day exposure. The hibernation season ended after 30-34 wk on short days, several weeks later than in testis-intact males studied previously. These results indicate that gonadal factors are not required for the termination of hibernation but may influence its timing. The resumption of FSH secretion occurred no later during short-day exposure in castrated hibernators than in the preceding study of testis-intact, short-day males hibernating in the cold or those held at room temperature. Thus the endogenous timing mechanism regulating the reactivation of the hypothalamopituitary axis toward the end of the winter season is apparently gonad independent and is little affected by the low body temperatures experienced during hibernation.

Pineal melatonin rhythms in female Turkish hamsters: effects of photoperiod and hibernation.

Daily rhythms of pineal and serum melatonin content were characterized for adult female Turkish hamsters (Mesocricetus brandti) exposed to long days (16L:8D, 22 degrees C) or after transfer to short days (10L:14D, 22 degrees C). The nocturnal peak of pineal melatonin content was found to be approximately 3 b greater in duration on short than on long days. Changes in levels of serum melatonin closely paralleled those of pineal melatonin. Thus, an effect of photoperiod on synthesis and secretion of pineal melatonin was demonstrated. In a separate experiment, female hamsters were induced to hibernate by exposure to a short-day, cold environment (10L:14D, 6 degrees C). During the 4 to 5-mo hibernation season, Turkish hamsters are known to display 4 to 8-day hours of torpor (body temperature = 7-9 degrees C) alternating with 1 to 3-day intervals of euthermia (body temperature = 35-37 degrees C). Little evidence of nocturnal synthesis or secretion of pineal melatonin was detected in females sampled during torpor. However, animals sampled during the first day after arousal from a torpor bout displayed melatonin rhythms no different in phase or amplitude from those seen in females held at 22 degrees C. Thus, despite the absence of pineal melatonin output during torpor, the pineal gland of hibernating Turkish hamsters produces an appropriately phased, rhythmic melatonin signal during intervals of euthermia.

Hemodynamic indicators of postthrombotic sequelae.

Single or repetitive episodes of lower-extremity venous thrombosis may result in venous obstruction, valvular incompetence, and the postthrombotic syndrome. Seventy-seven patients with ileofemoral deep venous thrombosis diagnosed with biplane phlebograms received routine anticoagulant therapy and follow-up with clinical and noninvasive vascular examinations (reflux photoplethysmography, Doppler ultrasonography, and venous outflow plethysmography). The results of the final visit (mean, 25 months; range, three to 50 months) revealed that 53 patients (69%) had evidence of edema and/or hyperpigmentation and five patients (6%) had ulceration. Doppler ultrasonography was 77% sensitive (41 of 53 patients) and 95% specific (41 of 43 patients) at identifying patients with postthrombotic sequelae. We conclude that noninvasive testing throughout the rehabilitative period following acute deep venous thrombosis will identify patients at risk for postthrombotic symptoms. This information may alert the clinician toward initiating elastic compressive therapy in hopes of prolonging a disease-free interval.

Shoulder harness traction for roentgenographic assessment of the cervical spine.

We evaluated the clinical usefulness of a new shoulder traction device to facilitate a rapid complete cervical spine examination in an uncooperative patient population with multiple trauma. Forty-eight patients were randomly designated to receive the shoulder traction device or the standard technique (manual traction on the patient's upper extremities). Patient groups were equivalent in mean coma scale scores, trauma scores, age, and incidence of cervical fracture. Male-female ratios differed between groups, yet were biased against the harness technique. Fewer roentgenograms (lateral view) were required to visualize adequately all cervical vertebrae when the harness device was utilized (mean roentgenograms per patient, 1.2 vs 2.6; P less than .01). Shoulder harness traction during roentgenographic evaluation of the cervical spine may be a useful method to promote visibility of the lower cervical vertebrae.

Effects of photoperiod, pinealectomy and castration on body weight and daily torpor in Djungarian hamsters (Phodopus sungorus).

During the autumn and winter Djungarian hamsters (Phodopus sungorus) exhibit regression of the gonads, development of a white winter pelage, loss of body weight and daily torpor. These seasonal events are largely regulated by changes in photoperiod. The present experiments were designed to examine the role of the testes and the pineal gland in photoperiodically induced daily torpor and body weight loss. Hamsters displayed a loss of body weight and daily torpor when exposed to a short-day photoperiod in a cold environment, but these phenomena did not occur in hamsters exposed to long days and cold. Testicular regression is probably a precondition for the display of torpor, since daily torpor was almost totally inhibited in hamsters which were exposed to short days and in which testosterone was administered from subcutaneous silicone elastomer implants. Nevertheless, decreased testosterone secretion alone is not a sufficient condition for induction of daily torpor, since torpor was rarely observed in hamsters exposed to long days, even after castration. In addition to decreased testicular activity, the pineal gland is also involved in establishing conditions for torpor. Thus, pinealectomy prevented the display of torpor by castrated hamsters exposed to short days. Body weight changes were also found to be influenced by both testicular hormone and pineal activity. These observations indicate that the pineal gland is involved, as a part of the photoperiodic mechanism, in regulating a variety of physiological events and that some of these actions of the pineal are independent of its extensively described actions on the reproductive axis.

Distal ulnar recession for disorders of the distal radioulnar joint.

Thirty-six wrists of 35 patients were treated with distal ulnar recession for pain and limitation of motion associated with chondromalacia of the ulnar head, triangular fibrocartilage complex tears, ulnocarpal impingement, and instability of the distal radioulnar joint. Contributing factors were positive ulnar variance in 31 wrists, fracture of the distal radius in five, sprains in 14, premature closure of the distal radial epiphysis in five, and lax ligamentous habitus in five. The ages of the patients averaged 33 years. Clinical findings were local tenderness, crepitus, and instability evident by a positive "piano key" effect. Roentgenographic findings were positive ulnar variance (29 of 36), zero ulnar variance (four), negative ulnar variance (three), positive arthrogram (11 of 19), and "forme fruste" Madelung's deformity (two). The surgical procedure is a modification of the Milch cuff resection with the use of a dynamic compression plate. Recession ranged from 2 to 13 mm (average of 4 mm). Findings at surgery included chondromalacia of the ulnar head (19), tears of the triangular fibrocartilage complex (11), and excessive mobility of the ulnar head (10). At an average follow-up of 24.5 months, results were excellent in 7 wrists, good in 21, fair in four, and poor in four. Poor results in two wrists were upgraded to good after osteosynthesis of a nonunion in one and recessional osteotomy of the radial sigmoid notch in the other. Ulnar recession offers a less destructive alternative to disorders of the distal radioulnar joint than the Darrach resection.

Circadian regulation of pineal melatonin and reproduction in the Djungarian hamster.

Gonadal state, pineal melatonin rhythms, and locomotor activity rhythms were examined in juvenile male Djungarian hamsters exposed to non-24-hr light cycles ("T-cycles") or to full photoperiods. At the end of 1 month, hamsters exposed to a 1-hr pulse of light every 24.33 hr (T 24.33) exhibited small testes, whereas those receiving the same amount of light every 24.78 hr (T 24.78) displayed stimulated gonads, ten-fold larger in size. Accompanying the nonstimulatory effect of the T 24.33 cycle were nocturnal peaks in both pineal melatonin content and serum melatonin concentration which were longer by approximately 4 hr than those observed on the photostimulatory T 24.78 cycle. Exposure to an intermediate-length T-cycle (T 24.53) resulted in a mixed gonadal response and in pineal and serum melatonin peaks of intermediate duration. Wheel-running activity was entrained to the T-cycles such that light was present only near the beginning of the subjective night, its phase (relative to activity onset) differing only slightly among T-cycle groups. Hence the durational differences observed in the melatonin peaks were apparently not due to the acute suppressive or phase-advancing effects of morning light on melatonin biosynthesis, but were rather the result of differences in the endogenous control of pineal activity by the circadian pacemaker system. While no strong correlation was detected between gonadal state and the phase of locomotor activity onset relative to the light pulse, a significant correlation was observed between gonadal state and the duration of daily locomotor activity (alpha). These data were compared to similar measures obtained from hamsters exposed to long-versus short-day full photoperiods (LD 16:8 vs. LD 10:14). In summary, the results of this study indicate involvement of the circadian pacemaker system of Djungarian hamsters in the control of pineal melatonin synthesis and secretion, and in photoperiodic time measurement. Furthermore, these data strengthen the hypothesis that it is the duration of nocturnal pineal melatonin secretion that is the critical feature of this neuroendocrine gland's photoperiodic signal.

Effects of timed melatonin infusions on reproductive development in the Djungarian hamster (Phodopus sungorus).

In confirmation of earlier work, daily melatonin infusions of 9- or 12-h duration inhibited testicular development in pinealectomized juvenile Djungarian hamsters, while daily infusions of 6-h duration did not prevent gonadal growth. Two other methoxyindoles (5-methoxytryptophol and 5-methoxytryptamine) had less than 4% of the activity shown by melatonin. When pinealectomized hamsters received two short duration (i.e. 3, 5, or 6 h) melatonin infusions each day, gonadal development was not inhibited if the two daily infusions were separated by a period of 2 or 3 h without melatonin treatment. Thus, the effects of separate pulses of melatonin were not additive in this paradigm. When single, short duration daily infusions of melatonin (5-h) or isoproterenol (6-h) were administered to pineal-intact hamsters, gonadal inhibition occurred only when the infusions were given at times that would lead to an expected overlap with and extension of the endogenous nocturnal melatonin peak. Significant inhibition of testicular growth could be obtained with as few as 2-4 days of melatonin treatment. These observations further support the importance of melatonin peak duration and also indicate other interesting temporal aspects of melatonin action in the Djungarian hamster.

The pineal gland and mammalian photoperiodism.

The mammalian pineal gland appears to be a major endocrine component in the regulation of photoperiodic responses. The circadian pattern of secretion of the pineal hormone, melatonin, is regulated by the nervous system. Changes in photoperiod, acting via the nervous system, alter the temporal pattern of melatonin secretion. The changes in secretion pattern convey information about daylength from neural components of the circadian system to the reproductive system, and probably to other physiological systems.

Circadian organization of locomotor activity in the Turkish hamster (Mesocricetus brandti).

The circadian organization of locomotor activity was examined in Turkish hamsters while exposed to a light-dark (LD) cycle, constant illumination (LL), and following blinding and gonadectomy. Under LD 16:8 the activity rhythm of all hamsters became well entrained with activity beginning approximately 30 min after dark onset. In contrast, when activity rhythms free-ran as the result of exposure to LL or blinding, a variety of spontaneous perturbations in the period and/or phase of the activity rhythm were observed.