A Model-Informed Drug Development Approach to Design a Phase 3 Trial of Teverelix Drug Product in Advanced Prostate Cancer Patients with Increased Cardiovascular Risk.

Teverelix drug product (DP) is a parenteral gonadotropin-releasing hormone (GnRH) antagonist that has been successfully tested in phase 2 trials for hormone-sensitive advanced prostate cancer (APC) and benign prostatic hyperplasia (BPH). In previous APC trials, teverelix DP was administered as intramuscular (IM) and subcutaneous (SC) injections, using a loading dose and (in a single trial) a maintenance dose. Our objective was to derive an optimal dosing regimen for phase 3 clinical development, using a pharmacometrics modeling approach. Data from 9 phase 2 studies (229 patients) was utilized to develop a population pharmacokinetic (PK) model that described the concentration profile accommodating both IM and SC routes of administration. A 2-compartment model with sequential first-order absorption (slow and fast) and lag times best described the PK profiles of teverelix following SC and IM administration. An indirect response model with inhibition of production rate was fit to describe testosterone (T) concentrations based on physiological relevance. The final population PK-pharmacodynamic model was used to conduct simulations of various candidate dosing regimens to select the optimal dosing regimen to achieve clinical castration (T < 0.5 ng/mL by day 28) and to sustain clinical castration for 26 weeks. Model simulation showed that a loading dose of 360 mg SC and 180 mg IM with a maintenance dose of 360 mg SC 6-weekly (Q6W) starting at day 28 can achieve a ≥95% castration rate up to 52 weeks. This dose regimen was selected for phase 3 clinical development, which includes cardiovascular safety assessment in comparison to a GnRH agonist.

Breaking the Mold: Surgical Exploration for Spinal Impalement Injury Without Neurological Deficit.

Spinal cord injuries (SCI) are a significant burden on society, particularly affecting the working population. Traumatic SCI can result from violent confrontations, involving firearms, knives, or edged weapons. Although surgical techniques for these injuries are not well defined, surgical exploration, decompression, and removal of the foreign body are currently indicated for patients with spinal stab wound injuries with neurologic impairment. We present a case of a 32-year-old male patient who presented to the emergency department with a stab injury with a knife. Radiographs and CT scans revealed a broken knife blade with a midline trajectory in the lumbar spine, moving toward the vertebral body of L2 occupying less than 10% of the intramedullary canal. The patient underwent surgery, and the knife was successfully extracted without any complications. Post-operative MRI showed no signs of cerebrospinal fluid (CSF) leak, and the patient did not exhibit any sensorimotor deficit. The acute trauma life support (ATLS) procedure must be followed while treating a patient with penetrating spinal trauma with or without neurological impairment. After availing appropriate investigations, any attempt to remove a foreign object should be done. Although spinal stab wound injuries are uncommon in developed nations, they continue to be a source of traumatic cord damage in underdeveloped countries. Our case highlights the successful surgical management of a spinal stab wound injury with a good outcome.

Osteochondromas at Unusual Sites- Case Series with Review of Literature.

INTRODUCTION: Osteochondromas are benign tumours of the skeletal system. Their commonplace of occurrence is around growing ends of long bones like lower end of femur and upper end of tibia, but literature describing their incidence around flat bones of body like pelvis, scapula and small bones of hand, foot is rare. CASE REPORT: We describe two cases of osteochondromas at unusual sites, one on the dorsal aspect of scapula and other at the base of first metatarsal. Patient with scapular osteochondroma had difficulty in sleeping in supine position while that with metatarsal osteochondroma had discomfort while walking. CONCLUSION: Depending on the site of occurrence, osteochondromas can give rise to different local symptoms. Possibility of osteochondroma should be kept in mind during differential diagnosis of bony swelling in flat bones as well as small bones.

Why did the FDA approve efavirenz 800 mg when co-administered with rifampin?

OBJECTIVES: Literature reports regarding the efficacy of efavirenz (EFV) 600 mg with rifampin (RIF) are not consistent. Evaluation of a drug-drug interaction (DDI) study and supportive semi-mechanistic population pharmacokinetic (PK) analyses were undertaken to help delineate this issue. DESIGN/METHODS: DDI study and supportive semi-mechanistic population PK analyses were provided by BMS. Population PK analysis was based on six studies with intensive EFV PK sampling. An ACTG study with sparse PK sampling was used for model evaluation. Simulations compared EFV exposure at various doses in combination with RIF to EFV exposures at 600 mg once daily (QD). Effects of CYP2B6 genotypes on the magnitude of EFV-RIF interaction were also explored. RESULTS: In DDI study, co-administering EFV 600 mg QD and RIF reduced mean EFV exposure by ~ 30%. Population PK model provided acceptable predictive performance of central tendency and variability for EFV C0, Cmax, and AUC. Simulations predicted that increasing EFV to 800 mg QD with RIF would result in EFV AUC and Cmax similar to EFV 600 mg QD alone. EFV AUC and Cmax were ~ 2 times higher in subjects with reduced function CYP2B6 genotypes. However, the RIF effect was consistent across all genotypes. EFV dose adjustment to 800 mg QD did not increase the risk of overexposure compared to 600 mg EFV QD within each genotype. CONCLUSION: Dose adjustment based on matching systemic exposure was recommended to mitigate the potential for sub-therapeutic EFV exposures. Our review did not reveal any safety concerns in subjects receiving EFV 800 mg QD with RIF.

Semi-mechanistic pharmacodynamic modeling for degarelix, a novel gonadotropin releasing hormone (GnRH) blocker.

An integrated semi-mechanistic pharmacodynamic (PD) model describing the relationship between luteinizing hormone (LH) and testosterone (T) after short-term administration of degarelix was developed. Data from three clinical studies involving, intravenous (IV) and subcutaneous (SC) dosing, in healthy male subjects were available. Degarelix pharmacokinetic (PK) data from all studies were modeled simultaneously. One intravenous study was used to develop the PD model and the two other studies (IV and SC dosing) were used to qualify the model. Degarelix PK follows a two-compartment model and exhibits flip-flop kinetics after subcutaneous dosing. Based on physiological mechanism, the gonadotropin releasing hormone (GnRH) time course was described using a pulsatile release model. A precursor-dependent pool model was used to describe the kinetics of LH in the pituitary and plasma compartment. In males, LH regulates T production in leydig cells. Degarelix inhibits the release of LH from the pool compartment to the plasma compartment leading to decreased T production. The plasma half-life of LH (2.6-3.3 hr) and T (2.7 hr) match well with the literature reports. The proposed PD model reasonably described the time course of LH and T including the LH rebound for short-term studies. The model predicted the time course of LH and T for the second IV and SC dosing studies very well. However, the long term simulations from the final model did not match with literature reports. A modification is suggested based on the physiological understanding of the system. The proposed novel modification to precursor models can be of general use for predicting long term responses.