Pharmacokinetics of Novel Plant Cell-Expressed Taliglucerase Alfa in Adult and Pediatric Patients with Gaucher Disease

Current Status of Pharmacokinetic Research in Children: A Systematic Review of Clinical Trial Records

BACKGROUND

Many medications have different pharmacokinetics in children than in adults. Knowledge about the safety and efficacy of medications in children requires research into the pharmacokinetic profiles of children's medicines. By analysing registered clinical trial records, this study determined how frequently pharmacokinetic data is gathered in paediatric drug trials.

METHODS

We searched for the pharmacokinetic data from clinical trial records for preterm infants and children up to the age of 16 from January 2011 to April 2022. The records of trials involving one or more drugs in preterm infants and children up to the age of 16 were examined for evidence that pharmacokinetic data would be collected.

RESULTS

In a total of 1483 records of interventional clinical trials, 136 (9.17%) pharmacokinetic data involved adults. Of those 136 records, 60 (44.1%) records were pharmacokinetics trials involving one or more medicines in children up to the age of 16. 20 (33.3 %) in America, followed by 19 (31.6 %) in Europe. Most trials researched medicines in the field of infection or parasitic diseases 20 (33.3%). 27 (48.2%) and 26 (46.4%) trials investigated medicines that were indicated as essential medicine.

CONCLUSION

The pharmacokinetic characteristics of children's drugs need to be better understood. The current state of pharmacokinetic research appears to address the knowledge gap in this area adequately. Despite slow progress, paediatric clinical trials have experienced a renaissance as the significance of paediatric trials has gained international attention. The outcome of paediatric trials will have an impact on children's health in the future. In recent years, the need for greater availability and access to safe child-size pharmaceuticals has received a lot of attention.

Quantitative assessment of the exposure-efficacy relationship of glucocerebrosidase using Markovian elements in Gaucher patients treated with enzyme replacement therapy

AIMS

The aims of this study are (i) to develop a population pharmacokinetic model of enzyme activity in Gaucher-type 1 (GD1) patients after intravenous administration of enzyme replacement therapy (ERT) and, (ii) to establish an exposure-efficacy relationship for bone marrow infiltration to propose dose adjustments according to patient covariate values.

MATERIALS AND METHODS

A prospective follow-up, semi-experimental multi-centre study was conducted in four hospitals to evaluate the pharmacokinetics, efficacy and safety of ERT in GD1 patients. 25 individuals with 266 glucocerebrosidase (GCase) observations in plasma and leukocytes and 14 individuals with 68 Spanish Magnetic Resonance Imaging (S-MRI) observations were enrolled.

RESULTS

A two concatenated compartments with zero-order endogenous production and first-order distribution (CL₁ =3.85 x10^-1 L/d) and elimination (CL₂ = 1.25 L/d) allowed to describe GCase observations in plasma and leucocytes, respectively. An exponential time-dependency (k_T =6.14 x10^-1 d^-1 ) effect on CL₁ was incorporated. The final exposure-efficacy model was a longitudinal logistic regression model with a first-order Markov element. An Emax function (EC₅₀ =15.73 U/L and Emax=2.33) linked steady-state concentrations of GCase in leucocytes to the probability of transition across the different S-MRI stages.

CONCLUSION

A population pharmacokinetic model successfully characterized the leukocyte activity-time profiles of GCase following intravenous administration of ERT in GD1 patients together with an exposure-efficacy relationship in bone marrow using markovian elements. The information obtained from this study could be of high clinical relevance in individualization of ERT in GD1 patients, as this could lead to anticipate decision-making regarding clinical response in bone and optimal dosing strategy. NONSTANDARD ABBREVIATIONS: -2LL: -2xlog(likelihood); ERT: enzyme replacement therapy; GCase: glucocerebrosidase activity; GD1: Gaucher disease type 1; GOF: goodness-of-fit plots; IIV: inter-individual variability; NLME: non-linear mixed effects modelling; OFV: objective function value; pc-VPC: prediction-corrected visual predictive check; PK: pharmacokinetic; RSE: relative standard error; RUV: residual unexplained variability, S-MRI: Spanish Magnetic Resonance Imaging, TDM: therapeutic drug monitoring.

Open-label, expanded access study of taliglucerase alfa in patients with Gaucher disease requiring enzyme replacement therapy

A multicenter, open-label, expanded-access study followed the safety of taliglucerase alfa, a plant cell-expressed recombinant enzyme replacement therapy (ERT), in adults with Gaucher disease previously treated with imiglucerase. Patients received taliglucerase alfa every 2 weeks for 9 months at a dose equivalent to their previous imiglucerase dose (Part A); patients were offered treatment for up to 33 months (Part B), and a later amendment allowed treatment-naïve patients. Fifty-eight patients received taliglucerase alfa (55.2% male; mean age, 46.1 years; mean bi-weekly dose, 35.2 U/kg; mean duration, 17.8 months); 51 patients previously received ERT, seven were treatment-naïve, and 36 completed the study. Most adverse events were mild or moderate; treatment-related adverse events were mild and transient. In previously treated patients, increases from baseline to last follow-up were observed for mean ± SE hemoglobin concentration (13.0 ± 0.3 g/dL to 13.4 ± 0.2 g/dL) and platelet count (179,242 ± 15,344/mm³ to 215,242 ± 17,867/mm³). Findings were similar in treatment-naïve patients (mean ± SE hemoglobin concentration and platelet count, 12.8 ± 0.3 g/dL to 13.5 ± 0.2 g/dL and 168,821 ± 14,368/mm³ to 204,641 ± 16,071/mm³, respectively). Taliglucerase alfa was well-tolerated for up to 33 months and demonstrated a durable therapeutic effect.

Relationship Between Glucocerebrosidase Activity and Clinical Response to Enzyme Replacement Therapy in Patients With Gaucher Disease Type I

The quantification of enzyme activity in the patient treated with enzyme replacement therapy (ERT) has been suggested as a tool for dosage individualization, so we conducted a study to evaluate the relationship between glucocerebrosidase activity and clinical response in patients with Gaucher disease type I (GD1) to ERT. The study included patients diagnosed with GD1, who were being treated with ERT, and healthy individuals. Markers based on glucocerebrosidase activity measurement in patients' leucocytes were studied: enzyme activity at 15 min. post-infusion (Act₇₅ ) reflects the amount of enzyme that is distributed in the body post-ERT infusion, and accumulated glucocerebrosidase activity during ERT infusion (Act_75-0 ) indicates the total drug exposure during infusion. The clinical response was evaluated based on criteria established by Pastores et al. and Gaucher Severity Score Index. Statistical analysis included ROC analysis and area under the curve test. Act₇₅ and Act_75-0 were found to be moderate predictive markers of an optimal clinical response (area under the ROC of Act₇₅ was 0.733 and Act_75-0 was 0.817). Act_75-0 showed statistical significance in its discriminative capacity (p < 0.05) for obtaining an optimal response to ERT. The cut-off point was 58% (RR = 1.800; 95% CI: 1.003-3.229; p < 0.05). Moreover, Act₇₅ showed a significant and inverse correlation with the Gaucher Severity Score Index, and Act₇₅ and Act_75-0 presented a significant correlation with residual enzyme activity at diagnosis. Markers based on glucocerebrosidase activity have a good correlation with clinical response to ERT. Therefore, it could provide supporting clinical data for dose management in GD1 patients.

Taliglucerase alfa: safety and efficacy across 6 clinical studies in adults and children with Gaucher disease

Taliglucerase alfa is an enzyme replacement therapy (ERT) approved for treatment of adult and paediatric patients with Type 1 Gaucher disease (GD) in several countries and the first plant cell-expressed recombinant therapeutic protein approved by the US Food and Drug Administration for humans. Here, we review the findings across six key taliglucerase alfa clinical studies. A total of 33 treatment-naïve adult patients were randomized to taliglucerase alfa 30 U/kg or 60 U/kg in a 9-month, multicentre, randomized, double-blind, parallel-group, dose-comparison pivotal study, after which eligible patients continued into two consecutive extension studies; 17 treatment-naïve adult patients completed 5 total years of treatment with taliglucerase alfa. In the only ERT study focused on exclusively paediatric patients with GD, 11 treatment-naïve children were randomized to taliglucerase alfa 30 U/kg or 60 U/kg in a 12-month, multicentre, double-blind study; nine completed 3 total years of treatment in a dedicated paediatric extension study. The effect of switching patients from imiglucerase to taliglucerase alfa was also investigated in a separate 9-month study that included 26 adults and five children; 10 adults completed a total of 3 years and two children completed a total of 2.75 years of taliglucerase alfa treatment in the extension studies. All studies evaluated safety and spleen volume, liver volume, platelet count, haemoglobin concentration, and biomarkers as measures of efficacy. Detailed results from baseline through the end of these studies are presented. Taliglucerase alfa was well tolerated, and adverse events were generally mild/moderate in severity and transient. Treatment with taliglucerase alfa resulted in improvements (treatment-naïve patients) or stability (patients switched from imiglucerase) in visceral, haematologic, and biomarker parameters. Together, this comprehensive data set supports the treatment of adult and paediatric patients with GD who are naïve to ERT or who have previously been treated with imiglucerase.

Hematopoietic stem cell transplantation for Gaucher disease

BACKGROUND

Gaucher disease is the most common lysosomal storage disorder caused by a deficiency of the enzyme glucocerebrosidase. Current treatment of the disease involves a choice from enzyme replacement therapy, substrate reduction therapy and hemotopoietic stem cell transplantation (HSCT). HSCT is a high risk procedure with possible long-term benefits in the regression of skeletal and neurological changes in people with Gaucher disease. This is an update of a previously published Cochrane Review.

OBJECTIVES

To determine the role of HSCT in people with Gaucher disease in relation to: mortality risk associated with the procedure; efficacy in modifying the course of the disease; and arrest or regression of neurological manifestations in neuronopathic forms (types 2 and 3).

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Inborn Errors of Metabolism Trials Register which comprises of references identified from comprehensive electronic database searches and handsearches of relevant journals and abstract books of conference proceedings.Date of the most recent search of the Group's Haemoglobinopathies Trials Register: 19 January 2017.We also searched the websites: www.clinicaltrials.gov; WHO International Clinical Trials Registry Platform portal and www.genzymeclinicalresearch.com. Date of most recent search of these sites: 02 March 2017.

SELECTION CRITERIA

All randomised, quasi-randomised and controlled clinical trials comparing stem cell transplantation with enzyme replacement therapy, substrate reduction therapy, symptomatic treatment or no treatment in people with Gaucher disease of all ages.

DATA COLLECTION AND ANALYSIS

We independently assessed trials for inclusion, however, no relevant trials were identified.

MAIN RESULTS

Thirty two trials were identified by the searches; however, these were not suitable for inclusion in the review.

AUTHORS' CONCLUSIONS

HSCT is a form of treatment that offers the potential of permanent cure. However, there are no clinical trials that have assessed the safety and efficacy of this treatment in comparison to other conservative measures (enzyme replacement therapy, substrate reduction therapy) now in use.There are no trials included in the review and we have not identified any relevant trials up to March 2017. We therefore do not plan to update this review until new trials are published.