Pharmacometric Analysis of the Relationship Between Absolute Lymphocyte Count and Expanded Disability Status Scale and Relapse Rate, Efficacy End Points, in Multiple Sclerosis Trials.

The aim of this work was to assess the relationship between the absolute lymphocyte count (ALC), and disability (as measured by the Expanded Disability Status Scale [EDSS]) and occurrence of relapses, 2 efficacy endpoints, respectively, in patients with remitting-relasping multiple sclerosis. Data for ALC, EDSS, and relapse rate were available from 1319 patients receiving placebo and/or cladribine tablets. Pharmacodynamic models were developed to characterize the time course of the endpoints. ALC-related measures were then evaluated as predictors of the efficacy endpoints. EDSS data were best fitted by a model where the logit-linear disease progression is affected by the dynamics of ALC change from baseline. Relapse rate data were best described by the Weibull hazard function, and the ALC change from baseline was also found to be a significant predictor of time to relapse. Presented models have shown that once cladribine exposure driven ALC-derived measures are included in the model, the need for drug effect components is of less importance (EDSS) or disappears (relapse rate). This simplifies the models and theoretically makes them mechanism specific rather than drug specific. Having a reliable mechanism-specific model would allow leveraging historical data across compounds, to support decision making in drug development and possibly shorten the time to market.

Application of Item Response Theory to Modeling of Expanded Disability Status Scale in Multiple Sclerosis.

In this study, we report the development of the first item response theory (IRT) model within a pharmacometrics framework to characterize the disease progression in multiple sclerosis (MS), as measured by Expanded Disability Status Score (EDSS). Data were collected quarterly from a 96-week phase III clinical study by a blinder rater, involving 104,206 item-level observations from 1319 patients with relapsing-remitting MS (RRMS), treated with placebo or cladribine. Observed scores for each EDSS item were modeled describing the probability of a given score as a function of patients' (unobserved) disability using a logistic model. Longitudinal data from placebo arms were used to describe the disease progression over time, and the model was then extended to cladribine arms to characterize the drug effect. Sensitivity with respect to patient disability was calculated as Fisher information for each EDSS item, which were ranked according to the amount of information they contained. The IRT model was able to describe baseline and longitudinal EDSS data on item and total level. The final model suggested that cladribine treatment significantly slows disease-progression rate, with a 20% decrease in disease-progression rate compared to placebo, irrespective of exposure, and effects an additional exposure-dependent reduction in disability progression. Four out of eight items contained 80% of information for the given range of disabilities. This study has illustrated that IRT modeling is specifically suitable for accurate quantification of disease status and description and prediction of disease progression in phase 3 studies on RRMS, by integrating EDSS item-level data in a meaningful manner.

Polyethylene glycol-conjugated growth hormone-releasing hormone is long acting and stimulates GH in healthy young and elderly subjects.

OBJECTIVE: The clinical use of growth hormone-releasing hormone (GHRH) is limited by its short half-life. Polyethylene glycol-conjugated GHRH (PEG-GHRH) was developed to provide increased stability compared with the currently available GHRH(1-29). This study aimed to evaluate the safety, tolerability and pharmacodynamics of PEG-GHRH. DESIGN: PEG-GHRH was administered by subcutaneous injection to young healthy men (n = 12) and elderly men and women (aged > 60 years; n = 20). RESULTS: In both groups, administration of PEG-GHRH generated a clear increase in circulating GH compared with placebo. Following single-dose (0.25, 0.5, 2 or 4 mg) administration to young subjects, the effect persisted for 12 h, but a sustained increase was observed on repeated administration to the elderly. Serum insulin-like growth factor-I also increased in response to PEG-GHRH treatment. Injection-site reactions were more frequent with PEG-GHRH compared with placebo, but these were mild and transient; other adverse events were similar to those observed after placebo. Some impairment of glucose tolerance was observed in the elderly following repeated administration of PEG-GHRH. Antibodies to GHRH were not observed. CONCLUSIONS: PEG-GHRH offers the possibility of less frequent dosing compared with GHRH. This possibility deserves further clinical testing.

Resistance Development: A Major Piece in the Jigsaw Puzzle of Tumor Size Modeling.

Mathematical models of tumor size (TS) dynamics and tumor growth inhibition (TGI) need to place more emphasis on resistance development, given its relevant implications for clinical outcomes. A deeper understanding of the underlying processes, and effective data integration at different complexity levels, can foster the incorporation of new mechanistic aspects into modeling approaches, improving anticancer drug effect prediction. As such, we propose a general framework for developing future semi-mechanistic TS/TGI models of drug resistance.

Pharmacometrics Markup Language (PharmML): Opening New Perspectives for Model Exchange in Drug Development.

The lack of a common exchange format for mathematical models in pharmacometrics has been a long-standing problem. Such a format has the potential to increase productivity and analysis quality, simplify the handling of complex workflows, ensure reproducibility of research, and facilitate the reuse of existing model resources. Pharmacometrics Markup Language (PharmML), currently under development by the Drug Disease Model Resources (DDMoRe) consortium, is intended to become an exchange standard in pharmacometrics by providing means to encode models, trial designs, and modeling steps.

A population model for the follicular growth in women treated with follicle stimulating hormone.

PURPOSE: To develop a pharmacodynamic model that can describe the time course of follicular growth and to investigate the influence, if any, of covariates on the parameters of the model. METHODS: A population pharmacodynamic analysis was performed on total follicular volume data obtained after in vitro fertilisation and embryo transfer with urinary or recombinant human follicle stimulating hormone (FSH) treatment. A growth model in which the increase in total follicular volume with time is a function of several possible components was chosen. RESULTS: In the final population pharmacodynamic model, increase in total follicular volume (TFV) was described by the equation: dTFV/dt = Emax.TFV/(TFV + TFV50) + constant, in which Emax, TFV50, and constant were 508 mm3/hr (interindividual variability 72%), 12,900 mm3 (66%), and 1.43 mm3/hr (91%), respectively. Growth was positively correlated to baseline estradiol levels, so that Emax and TFV50 changed 0.52% for every picomolar change from the median baseline estradiol value of 100 pmol/L. Growth was negatively correlated to pretreatment FSH levels, so that individuals with a median FSH (6.7 IU/L) were expected to have a fivefold higher total follicular volume at day 10 after the start of treatment, compared to individuals at the high end of the pretreatment FSH range (12 IU/L). No relationship between FSH concentration and follicular growth was found. The urinary versus recombinant origin of the drug did not influence the ovarian response. CONCLUSION: Women with high endogenous levels of FSH respond less to standard doses of exogenous FSH. Women with higher baseline levels of estradiol have larger expected follicular growth rates.

Disposition and irreversible plasma protein binding of tolmetin in humans.

The pharmacokinetics and irreversible plasma protein binding of tolmetin were studied in six healthy subjects after the administration of a single, 400 mg dose of tolmetin. With HPLC analysis, tolmetin, tolmetin glucuronide, and the isomers of tolmetin glucuronide, which result from intramolecular acyl migration in vivo, were detected in the plasma up to 4 hours after administration, whereas these conjugates were present in the urine up to 24 hours. Irreversible binding of tolmetin to plasma proteins occurred in all subjects. Irreversible binding exhibited a better correlation with exposure to tolmetin glucuronide (r = 0.5618) and the isomers of tolmetin glucuronide (r = 0.8200) than with exposure to tolmetin (-0.3635). This is consistent with the hypothesis that covalent binding occurs via the acyl glucuronide.

Absence of metabolic effects of the topical carbonic anhydrase inhibitors MK-927 and sezolamide during two-week ocular administration to normal subjects.

Potential systemic effects of the racemic carbonic anhydrase inhibitor MK-927 and its S-enantiomer, sezolamide hydrochloride, after topical ocular administration were investigated in a double-masked, randomized, placebo-controlled study in 16 healthy volunteers. A controlled diet was started 4 days before initiation of treatment and continued throughout the study. For 14 days six volunteers received bilaterally one drop of 2% MK-927 (1.2 mg) q.i.d., six received one drop of 1.8% sezolamide (1.1 mg) q.i.d., and four received the common vehicle q.i.d. Blood and urine electrolytes and acid-base profiles were measured before and on days 1, 7, and 14 of treatment, and 24-hour urine samples were collected daily. All values were compared with those on the pretreatment day. Taking the circadian variations of the parameters into account, no significant treatment effect was observed in either the daily profiles or the 14-day cumulative sodium, potassium, and citrate excretions. Because the usual variability of the measured biologic parameters has been reduced markedly by the stringent requirements of this study, it can be concluded that the induction of clinically significant metabolic changes by topically administered MK-927 or sezolamide is unlikely.

Drug concentration response relationships in normal volunteers after oral administration of losartan, an angiotensin II receptor antagonist.

The aim of this study was to investigate the relationships between plasma concentrations of losartan, an orally active angiotensin II inhibitor, its active metabolite EXP3174, and angiotensin II blockade. Six healthy subjects received single oral doses of 40, 80, or 120 mg losartan and placebo at 1-week intervals in a crossover study. Angiotensin II blockade was assessed by the blood pressure response to exogenous angiotensin II before and after losartan administration. EXP3174 reached higher plasma concentrations and was eliminated more slowly than its parent compound; its levels paralleled the profile of angiotensin II blockade closer than losartan. Inhibition of the pressure response was dose dependent. The Hill-shaped relationship between response and EXP3174 concentration (or time-integrated variables) approached a plateau with 80 mg. The dose-dependent increase in plasma renin and angiotensin II exhibited a considerable individual scatter. We conclude that losartan produces a dose-dependent, effective angiotensin II blockade that is largely determined by the active metabolite EXP3174.

Pharmacokinetics and pharmacodynamics of IFN-beta 1a in healthy volunteers.

The pharmacokinetics of recombinant human interferon-beta1a (IFN-beta1a) (Rebif, Ares-Serono, Geneva, Switzerland) were investigated in healthy volunteers following intravenous (i.v.) administration of increasing single doses of the drug (22 microg/6 million international units [MIU], 44 microg/12 MIU, and 66 microg/18 MIU); i.v., intramuscular (i.m.), and subcutaneous (s.c.) administration of a 66-microg dose; and repeated s.c. administration of four 66-microg doses at 48-h intervals. The disposition of IFN-beta1a followed triexponential decay after i.v. administration (half-lives 3 min, 42 min, and 22 h, respectively). After s.c. and i. m. administration, absorption was the rate-limiting factor in the terminal phase. The median absolute bioavailabilities were 30% and 27%, respectively. The accumulation ratio after repeated s.c. injections was 2.4, and a terminal half-life of 66 h was observed. Intracellular 2-5A synthetase activity and serum neopterin and beta2-microglobulin concentrations increased after all IFN-beta1a injections and remained elevated following every-other-day administration. The local tolerance was good, and the systemic tolerance was satisfactory.

Influence of interferon beta-1a dose frequency on PBMC cytokine secretion and biological effect markers.

Interferon-beta regimens for immune-mediated diseases, such as multiple sclerosis (MS), have not been compared regarding their biological effects. In this randomized, parallel-group, placebo-controlled study, cytokine secretion by mitogen-stimulated PBMCs and serum response markers were assessed in volunteers receiving subcutaneous recombinant IFN beta-1a (Rebif, Ares-Serono) 22 microg once a week (QW), 22 microg three times a week, 66 microg QW, or placebo. The production of IL-1beta, IL-6, IFN-gamma, TNF-alpha and TNF-beta markedly decreased during 24-48 h after each injection, with limited dose-dependency and no evidence of tolerance or effect augmentation over 1 month. IL-10 secretion remained unchanged. The increase in serum beta2-microglobulin, neopterin and 2-5A-synthetase was more sustained. Thus, IFN-beta-induced immunomodulation in vivo strongly depends on the administration schedule, the time-integrated effect being 2-3 times greater when a same weekly dose is divided in three injections.

Renal effects of nimesulide in furosemide-treated subjects.

In clinical settings where effective plasma volume is decreased, nonsteroidal anti-inflammatory drugs (NSAIDs) may induce acute renal failure. We have evaluated the effects of single and repeated doses of nimesulide on renal haemodynamics and electrolyte excretion in 8 healthy volunteers during a prolonged course of furosemide (frusemide). Under these study conditions, renal prostaglandin synthesis is expected to be elevated, with renal function being dependent upon increased levels of prostaglandins. Nimesulide induced an acute but transient decrease in indices of renal haemodynamics. Furosemide-induced increases in plasma renin activity and aldosterone levels were blunted, and urinary excretion of prostaglandin E2 was markedly reduced by nimesulide. The magnitude and time course of the natriuretic, kaliuretic and diuretic effects of furosemide were attenuated by nimesulide. Although the transient nature of the observed renal haemodynamic changes suggests that the risk of developing acute renal failure is small, the rise should be taken into account in patients with renal dysfunction. Sodium and potassium retention, and the blunting of the diuretic-induced electrolyte excretion, could be of clinical relevance. Nimesulide appears, therefore, to share the prostaglandin-dependent renal effects of other NSAIDs.

Clinical experience with angiotensin II receptor antagonists.

This series of studies was designed to assess in normal volunteers the relationships between various doses (5, 10, 20, 40, 80, and 120 mg) of the orally active angiotensin II antagonist losartan (DuP 753, MK-954) and their inhibitory effect on the pressure response to a given bolus of angiotensin I or II. It was found that the maximal inhibitory effect was reached with a dose of 80 mg. The minimal dose necessary for maximal efficacy would therefore be expected to be between 40 and 80 mg. The effect lasted for more than 24 h and was related almost exclusively to the circulating levels of the active metabolite EXP3174. It remains to be demonstrated in hypertensive patients that the same dose relationship holds for the antihypertensive effect, but preliminary data already suggest that this is the case.

Sinistrin clearance for determination of glomerular filtration rate: a reappraisal of various approaches using a new analytical method.

Several approaches are available to estimate the glomerular filtration rate (GFR) from the sinistrin clearance. To compare such approaches, GFR was estimated in six healthy volunteers, both after a bolus injection and a bolus dose followed by a 6-hour infusion. A recently developed high-performance liquid chromatography method was used for the determination of sinistrin levels, enabling precise measurements in plasma and urine samples with high sensitivity. Blood and urine were sampled up to 6 hours. Four calculation methods for estimating GFR were applied: 1) classical ratio of urinary excretion rate over plasma concentration (UV/P); 2) two-point (log-linear regression slope times monocompartmental volume of distribution) after bolus; 3) ratio of dose over area under the curve (D/AUC) after bolus; and 4) ratio of infusion rate over steady-state concentration during infusion (Rinf/P). The results obtained by fitting a pharmacokinetic model to all the plasma and urine data served as the standard against which the performance of the respective calculation methods were examined. The UV/P method performed poorly on bolus data, mainly by underestimating GFR at late times; on both bolus and infusion data, it suffered from important imprecisions on the urinary volume. The two-point method appeared applicable only between 2 and 4 hours after the bolus dose. The D/AUC method with extrapolation to infinity was highly reliable when integrating the concentrations up to 3 hours or more after the bolus dose. The Rinf/P method was satisfactory if applied later than 2 to 3 hours after the loading dose. The advantages and drawbacks of each method have to be evaluated in relation to the particular clinical setting in which GFR is to be estimated.

Prevention of arrhythmias after noncardiac thoracic operations: flecainide versus digoxin.

Cardiac arrhythmias are known complications of thoracic operations. The prophylactic value of flecainide administered as a constant-rate, intravenous infusion (0.15 mg.kg-1.h-1) after a loading dose (2 mg.kg-1) was compared with digoxin (10 micrograms.kg-1 for 12 hours, then 0.25 mg.24 h-1) in a randomized study in 30 patients using Holter monitoring during the first 72 hours after operation. Drug monitoring was performed every day to keep a serum level of flecainide of 200 to 600 ng.mL-1 and a digoxin level of 0.8 to 2 ng.mL-1. Failure, defined as the appearance of atrial fibrillation or flutter or the development of complex ventricular arrhythmias (Lown IVb and V), was observed in one patient in the flecainide group (7%) and in 7 patients in the digoxin group (47%) (p less than 0.05). It is concluded that flecainide is more efficient than digoxin in preventing and treating cardiac arrhythmias after thoracic operations. At the dosage used side effects related to flecainide or digoxin were not observed.

Leukemia inhibitory factor in human reproduction.

OBJECTIVE: To describe the clinical findings, expressions, interactions, and clinical implications of leukemia inhibitory factor (LIF) in human reproduction. DESIGN: Review of published articles. SETTING: Clinical development unit of biotechnology company. INTERVENTION(S): None. RESULT(S): In the endometrium, LIF is expressed in a menstrual cycle-dependent manner, with the highest level occurring at the time of implantation. LIF is also detected in uterine flushing, and its level is significantly lower in women with unexplained infertility. Likewise, endometrial explants derived from women with unexplained infertility showed reduced levels of LIF secretion. Binding of LIF to LIF receptor and gp130 activates signal transduction pathways. LIF receptor is expressed in endometrium, oocytes, and blastocysts. Cytotrophoblasts cultured in the presence of LIF differentiate toward an anchoring extravillous phenotype. CONCLUSION(S): On the basis of reports gathered from animal and human studies, LIF appears to play an important role in implantation and in the establishment of pregnancy.

Clinical pharmacology of recombinant human luteinizing hormone: Part I. Pharmacokinetics after intravenous administration to healthy female volunteers and comparison with urinary human luteinizing hormone.

OBJECTIVE: To assess the pharmacokinetics after i.v. administration of a recombinant human LH and to compare them to those of a reference hMG preparation containing urinary human LH. DESIGN: Prospective, dose-escalating, cross-over study. SETTING: Phase I clinical research environment. PATIENT(S): Twelve healthy pituitary down-regulated females. INTERVENTION(S): Subjects received single i.v. doses of 300, 10,000, and 40,000 IU of recombinant human LH, followed by a single i.v. dose of 300 IU of hMG, all separated by 1 week. MAIN OUTCOME MEASURE(S): Pharmacokinetic parameters. RESULTS: For both preparations, LH serum levels were well described by similar biexponential models. The pharmacokinetics of recombinant human LH were linear over the 300 to 40,000 IU range. After a rapid distribution phase with an initial half-life of 1 hour, both recombinant human LH and urinary human LH were eliminated with a terminal half-life of 10-12 hours. Total serum clearance was 1.7 L/h with < 4% and 30% of the dose being eliminated in the urine for recombinant human LH and urinary human LH, respectively. The volume of distribution at steady-state was approximately 10 L. Irrespective of the dose, recombinant human LH was well tolerated. CONCLUSION(S): The pharmacokinetics of recombinant human LH are linear with dose and similar to those of urinary human LH.

Clinical pharmacology of recombinant human luteinizing hormone: Part II. Bioavailability of recombinant human luteinizing hormone assessed with an immunoassay and an in vitro bioassay.

OBJECTIVE: To assess the single-dose pharmacokinetics of a recombinant human LH preparation administered by the i.v., i.m., and s.c. route. DESIGN: Prospective, randomized cross-over study. SETTING: Phase I clinical research environment. PATIENT(S): Twelve healthy pituitary down-regulated females. INTERVENTION(S): Subjects received single i.v., i.m., and s.c. doses of 10,000 IU of recombinant human LH, each separated by 1 week. MAIN OUTCOME MEASURE(S): Pharmacokinetic parameters. RESULT(S): After single i.v. administration, the pharmacokinetics were described by a two-compartment model, after i.m. or s.c. administration, by a one-compartment model with zero order absorption and a lag time. Using the immunoassay, after i.v. administration initial half-life was 1 hour and terminal half-life was 10 hours (half-life was prolonged after extravascular administration, suggesting rate-limiting absorption). Total serum clearance was 2.6 L/h, and steady, state volume of distribution was 14 L. Observed Cmax, after i.m. and s.c. administration, was 43 IU/L with median tmax of 9 hours (i.m.) and 5 hours (s.c.). Bioavailability was 0.54 (i.m.) and 0.56 (s.c.). The pharmacokinetics of LH are comparable using an in vitro bioassay. CONCLUSION(S): The terminal half-life of recombinant human LH is around 12 hours and is slightly prolonged after extravascular administration. The pharmacokinetics are similar after i.m. and s.c. injection, and one-half the administered dose is available systemically.

Pharmacokinetic and pharmacodynamic interactions between recombinant human luteinizing hormone and recombinant human follicle-stimulating hormone.

OBJECTIVE: To assess the pharmacokinetics of a recombinant human LH preparation and its pharmacokinetic and pharmacodynamic interactions with recombinant human follicle-stimulating hormone (FSH). DESIGN: Prospective, randomized cross-over study. SETTING: Phase I clinical research environment. PATIENT(S): Twelve healthy pituitary down-regulated females. INTERVENTION(S): Subjects received 150 IU of s.c. recombinant human LH and FSH, either alone or in combination, followed by recombinant human LH and FSH once daily for 7 days. MAIN OUTCOME MEASURE(S): Pharmacokinetic parameters, ovarian follicle development. RESULT(S): No pharmacokinetic interaction between recombinant human LH and FSH was observed, with no significant difference in baseline-corrected maximal observed concentration over baseline, area under the concentration-time curve from t = 0 to t = 24 hours, or time to maximal concentration after single doses alone or in combination. After daily administration, the mean accumulation ratio was 1.6 for LH and 2.9 for FSH, with absorption and terminal phase half-life estimates of 4 and 11 hours for LH and 8 and 16 hours for FSH, respectively. Combined administration of FSH and LH for 7 days was effective in stimulating ovarian follicular development and steroidogenesis, with large interindividual variability related to ovarian sensitivity. CONCLUSION(S): A new recombinant human LH preparation has a low accumulation ratio at steady-state and no pharmacokinetic or pharmacodynamic interactions with recombinant human FSH.

Comparative pharmacokinetics and pharmacodynamics of recombinant human interferon beta-1a after intramuscular and subcutaneous administration.

The pharmacokinetics and pharmacodynamics of recombinant human interferon beta (IFN-beta-1a) were compared after intramuscular administration of two preparations (Rebif(R) and AvonexTM) and subcutaneous administration of Rebif(R). Healthy volunteers (n = 30) received a single dose (60 µg) of each of the three treatments in a randomised crossover study. Serum concentrations of IFN-beta were measured by enzyme-linked immunosorbent assay over 24 h after dosing. Pharmacodynamics were assessed by measurement of intracellular 2',5'-oligoadenylate synthetase activity, and serum neopterin and beta2-microglobulin concentrations, over 144 h after dosing. There was no significant difference between the three treatments in peak serum IFN-beta concentrations (Cmax) or area under the concentration-time curve (AUC). No significant differences in pharmacodynamic measures were observed between the three treatments. It is concluded that the bioavailability of IFN-beta-1a is equivalent after subcutaneous or intramuscular administration of Rebif(R), and intramuscular administration of AvonexTM. Copyright Rapid Science Ltd