Rituximab pediatric drug development: Pharmacokinetic and pharmacodynamic modeling to inform regulatory approval for rituximab treatment in patients with granulomatosis with polyangiitis or microscopic polyangiitis

Anti-neutrophil cytoplasmic antibody-associated vasculitides granulomatosis with polyangiitis (GPA) and microscopic polyangiitis (MPA) are rare, potentially organ- and life-threatening autoimmune conditions affecting adult and pediatric patients. An open-label phase II study was conducted to determine safe and effective dosing regimens of rituximab in pediatric patients with GPA/MPA. To determine the selection of an appropriate dose regimen in children for induction and maintenance, a population pharmacokinetic approach was used (nonlinear mixed-effect modeling), combining pediatric data with data from adults with GPA/MPA. The time course of B-cell depletion was assessed in both populations. The exposure-effect relationship was assessed by logistic regression. Twenty-five pediatric patients (80% female patients; age range, 6-17 years) were enrolled in the trial and received the induction regimen of intravenous rituximab 375 mg/m² weekly for 4 weeks, which resulted in a similar exposure to that of adults. Based on pharmacokinetic modeling, a maintenance dosing regimen of 250 mg/m² administered twice over 14 days followed by 250 mg/m² every 6 months is expected to result in similar rituximab exposure as that of adults receiving the approved maintenance dose of 500 mg administered twice over 14 days followed by 500 mg every 6 months. The time course of B-cell depletion was similar between the pediatric and adult populations, supporting the similarities in response in both populations and allowing extrapolation to patients less than 6 years old. Using a partial extrapolation approach helped identify safe and effective dosing regimens of rituximab in pediatric patients with GPA/MPA and lead to regulatory approval.

Phase IIa Global Study Evaluating Rituximab for the Treatment of Pediatric Patients With Granulomatosis With Polyangiitis or Microscopic Polyangiitis

Objective

To assess the safety, tolerability, pharmacokinetics, and efficacy of rituximab (RTX) in pediatric patients with granulomatosis with polyangiitis (GPA) or microscopic polyangiitis (MPA).

Methods

The Pediatric Polyangiitis Rituximab Study was a phase IIa, international, open‐label, single‐arm study. During the initial 6‐month remission‐induction phase, patients received intravenous infusions of RTX (375 mg/m² body surface area) and glucocorticoids once per week for 4 weeks. During the follow‐up period, patients could receive further treatment, including RTX, for GPA or MPA. The safety, pharmacokinetics, pharmacodynamics, and exploratory efficacy outcomes with RTX were evaluated.

Results

Twenty‐five pediatric patients with new‐onset or relapsing disease were enrolled at 11 centers (19 with GPA [76%] and 6 with MPA [24%]). The median age was 14 years (range 6–17 years). All patients completed the remission‐induction phase. During the overall study period (≤4.5 years), patients received between 4 and 28 infusions of RTX. All patients experienced ≥1 adverse event (AE), mostly grade 1 or grade 2 primarily infusion‐related reactions. Seven patients experienced 10 serious AEs, and 17 patients experienced 31 infection‐related AEs. No deaths were reported. RTX clearance correlated with body surface area. The body surface area–adjusted RTX dosing regimen resulted in similar exposure in both pediatric and adult patients with GPA or MPA. Remission, according to the Pediatric Vasculitis Activity Score, was achieved in 56%, 92%, and 100% of patients by months 6, 12, and 18, respectively.

Conclusion

In pediatric patients with GPA or MPA, RTX is well tolerated and effective, with an overall safety profile comparable to that observed in adult patients with GPA or MPA who receive treatment with RTX. RTX is associated with a positive risk/benefit profile in pediatric patients with active GPA or MPA.

SAT0503 SERIOUS INFECTION RISK IN PEDIATRIC PATIENTS WITH LOW IMMUNOGLOBULIN LEVELS FOLLOWING RITUXIMAB TREATMENT FOR GRANULOMATOSIS WITH POLYANGIITIS (GPA) OR MICROSCOPIC POLYANGIITIS (MPA)

Background:

Low immunoglobulin (Ig) levels can occur after rituximab treatment, but the clinical significance is not completely understood. Not all patients (pts) who develop low Ig levels after rituximab are at an increased risk of serious infection (SI), but factors such as pre-existing low Ig levels, prior biologic therapies, history of SI and other disease and age-related factors may increase the risk.

Objectives:

To assess the risk of SI in pediatric pts with prolonged low IgG or IgM serum concentrations following rituximab treatment for GPA or MPA in a global clinical trial.

Methods:

In the Phase 2a PePRS study (WA25615), pts aged ≥ 2 to ≤ 18 yrs with GPA or MPA received 4 weekly intravenous rituximab infusions of 375 mg/m2body surface area and concomitant oral glucocorticoid taper. After 6 months, pts could receive further rituximab and/or other immunosuppressants at the investigator’s discretion during a minimum 12-month follow-up phase. Pts with IgG/IgM levels below age-specific reference ranges at baseline were excluded. Ig levels were measured every 4-12 wks. SI occurrence was assessed during/after low IgG or IgM. Prolonged low Ig was defined as IgG or IgM levels < lower limit of normal (LLN) reference range for age for a ≥ 4-month period.

Results:

All 25 pts completed 4 weekly rituximab infusions and the 6-month Remission Induction Phase; 24/25 pts completed ≥ 18 months of follow-up. 17 pts received additional rituximab treatment on or after Month 6. 11 pts received concomitant immunosuppressants (cyclophosphamide, azathioprine, mycophenolate mofetil) during the study. All pts had a decrease in IgG and IgM mostly after the first rituximab infusion. There was no consistent trend in IgG or IgM levels over time and no clear relationship between low IgG or IgM levels and the number of follow-up rituximab treatments. 18 pts (72%) had prolonged low IgG ≥ 4 months, of whom 5 had IgG levels < LLN at screening and/or baseline; in 7 pts, IgG levels returned to within normal range by study end. During or after prolonged low IgG, 6/18 pts experienced a total of 7 SIs. Three pts received treatment with intravenous Ig. 19 pts (76%) had prolonged low IgM, of whom 5 had IgM levels < LLN at screening and/or baseline. During or after prolonged low IgM levels, 6/19 pts experienced a total of 8 SIs. There were no deaths or study discontinuation due to SI. All pts with prolonged low IgG or IgM had past and/or concomitant treatment with steroids and/or immunosuppressants as potential contributory factors. Analysis of SI onset in relation to timing of low Ig was limited due to protocol-defined time points for Ig assessments.

Conclusion:

In pediatric pts with GPA/MPA treated with rituximab, there was no consistent pattern in IgG or IgM levels over time. The majority of pts with prolonged low IgG or IgM did not experience any SIs; no increase in the number of SIs was observed over time or with multiple rituximab treatments. While no firm conclusions can be made on a possible relationship between prolonged low IgG or IgM and risk of SI following rituximab due to study limitations (low pt numbers, lack of placebo comparator), these observations are consistent with the known rituximab safety profile in adult pts with GPA/MPA.

Disclosure of Interests:

Simone Melega Shareholder of: F. Hoffmann-La Roche, Employee of: F. Hoffmann-La Roche, Paul Brogan Grant/research support from: Roche, Novartis, SOBI, Chemocentryx, Novimmune, Consultant of: Roche, SOBI, UCB, Novartis, Speakers bureau: Roche, SOBI, UCB, Novartis, Gavin Cleary Speakers bureau: AbbVie, Aimee Hersh: None declared, Ozgur Kasapcopur: None declared, Satyapal Rangaraj: None declared, Rae Yeung Consultant of: AbbVie, Novartis, Speakers bureau: AbbVie, Novartis, Andrew Zeft: None declared, Jennifer Cooper Employee of: Genentech, Inc., Pooneh Pordeli Shareholder of: Roche, Employee of: Roche, Petra Kirchner Shareholder of: Roche, Employee of: Roche, Patricia Lehane Shareholder of: Roche, Employee of: Roche

Risk of Malignancies in Patients with Rheumatoid Arthritis Treated with Rituximab: Analyses of Global Postmarketing Safety Data and Long-Term Clinical Trial Data

INTRODUCTION

Patients with rheumatoid arthritis (RA) are at an increased risk of developing malignancies, but it is unclear whether this increased risk is the result of disease pathobiology or immunosuppressant treatments for RA. This analysis evaluated the potential risk of malignancy in patients with RA treated with rituximab (MabThera®/Rituxan®) a CD20+ B-cell depleting agent manufactured by F. Hoffmann-La Roche Ltd.

METHODS

Malignancy rates were obtained from the rituximab global company safety database for adverse event reporting and from the rituximab global clinical trial program for RA consisting of eight randomized clinical trials, two long-term open-label extensions, and one open-label prospective study. Global company safety database searches were performed using the standard Medical Dictionary for Regulatory Activities (MedDRA) queries "Malignant tumors wide" and "Skin malignant tumors wide" up to April 30, 2017. Age- and sex-specific comparator values from the general population were obtained from the US National Cancer Institute Surveillance, Epidemiology, and End Results (SEER) database.

RESULTS

For the 409,706 patients with RA in the rituximab global company safety database since first market approval in 2006, 1739 cumulative malignant events were reported, with an overall malignancy reporting rate of approximately 4.2 events per 1000 patients. No evidence of increased risk of malignancy, of any organ-specific type, was found following rituximab treatment. The rate of malignancies from rituximab-treated patients in RA clinical trials was 7.4 per 1000 patient-years. This is within the expected range, with no evidence for increased risk over time or with additional rituximab courses.

CONCLUSIONS

Analyses of the global postmarketing safety database and long-term clinical trial data showed no evidence of an increased risk of malignancy of any type following rituximab treatment in patients with RA.

FUNDING

F. Hoffmann-La Roche Ltd.

Rituximab utilization for approved and off-label nononcology indications and patients' experiences with the Patient Alert Card

This study used retrospective chart review and survey data to evaluate: (1) off-label use of rituximab (MabThera®/Rituxan®) in autoimmune conditions and (2) patients' receipt and knowledge of the Patient Alert Card (PAC), a risk minimization measure for progressive multifocal leukoencephalopathy (PML) and serious infections. Anonymized patient data were collected from infusion centers in Europe from December 2015 to July 2017. Adults receiving rituximab in the same centers were provided a self-administered survey. Outcomes included patterns of off-label rituximab use for nononcology indications, and evaluation of patients' receipt and knowledge of the PAC and its impact. Of 1012 patients in the retrospective chart review, 70.2% received rituximab for rheumatoid arthritis or granulomatosis with polyangiitis/microscopic polyangiitis, and 29.8% received rituximab off label. Among 524 survey participants, 32.8% reported receiving the PAC, 59.3% reported not receiving the PAC and 7.9% did not know whether they received the PAC. A total of 72.4% of patients reported that they were unaware that some patients receiving rituximab experience PML. A higher proportion of PAC recipients identified PML as a potential risk of rituximab than nonrecipients (37.8% vs 19.9%); 58.3% of PAC recipients had poor awareness of PML. Most PAC recipients (90.0%) and nonrecipients (85.5%) correctly answered that they should seek medical attention for infection symptoms. In conclusion, approximately 30% of patients received off-label rituximab. Most patients reported not receiving the PAC or having knowledge of PML but demonstrated understanding of the recommended action in the event of infection symptoms, regardless of PAC receipt.

Anti-diabetic properties of a non-conventional radical scavenger, as compared to pioglitazone and exendin-4, in streptozotocin-nicotinamide diabetic mice

We previously showed that the innovative radical scavenger bis(1-hydroxy-2,2,6,6-tetramethyl-4-piperidinyl)-decandioate (IAC) improves metabolic dysfunctions in a diabetic mouse model. Here, we compared the in vivo effects of IAC with those of the anti-diabetic drugs pioglitazone (PIO) and exendin-4 (EX-4). Diabetes was induced in C57Bl/6J mice by streptozotocin and nicotinamide administration. Paralleled by healthy controls, diabetic animals (D) were randomly assigned to four groups and treated daily for 7 consecutive weeks: D+saline, ip; D+IAC 30mg/kgb.w., ip; D+PIO 10mg/kgb.w. per os; and D+EX-4, 50μg/kgb.w., ip. Our results show that IAC reduced basal hyperglycemia and improved glucose tolerance better than PIO or EX-4. Interestingly, in the heart of diabetic mice, IAC treatment normalized the increased levels of GSSG/GSH ratio and thiobarbituric acid reactive substances, indexes of oxidative stress and damage, while PIO and EX-4 were less effective. As supported by immunohistochemical data, IAC markedly prevented diabetic islet β-cell reduced density, differently from PIO and EX-4 that had only a moderate effect. Interestingly, in diabetic animals, IAC treatment enhanced the activity of pancreatic-duodenal homeobox 1 (PDX-1), an oxidative stress-sensitive transcription factor essential for maintenance of β-cell function, as evaluated by quantification of its nuclear immunostaining, whereas PIO or EX-4 treatments did not. Altogether, these observations support the improvement of the general redox balance and β-cell function induced by IAC treatment in streptozotocin-nicotinamide diabetic mice. Furthermore, in this model, the correction of diabetic alterations was better obtained by treatment with the radical scavenger IAC than with pioglitazone or exendin-4.

Effect of sprout extract from Tuscan black cabbage on xenobiotic-metabolizing and antioxidant enzymes in rat liver

In recent years, health protection by natural products has received considerable attention, and a multitude of nutraceuticals have been characterized and their use promoted. Dietary consumption of Cruciferous vegetables, rich in glucosinolates (GLs), and their myrosinase-mediated hydrolysis products isothiocyanates (ITCs), were associated with reductions in cancer risk. In this study, the chemo-preventive potential of sprout extract of Tuscan black cabbage (Brassica oleracea L. var. acephala subvar. Laciniata L.) (TBCSE), through modulation of the xenobiotic-metabolizing apparatus and antioxidant defenses, was investigated in Sprague-Dawley rat liver. TBCSE was administered either orally or intraperitoneally, at a dose of 15mg/kg b.w., daily for twenty-one consecutive days, in the absence or presence of exogenous myrosinase, β-thioglucoside glucohydrolase (MYR), to distinguish the effects of intact GLs and ITCs, in the context of the extract. A complex, mild modulation pattern of P450-related monooxygenases was observed, mainly regarding CYP content (up to 36% loss), NADPH cytochrome (P450) c-reductase (up to 26% loss), CYP1A1 (up to 23% loss), but no evident distinctions among the effects of the extracts containing GLs or ITCs, were noted. In contrast, significant inductions of phase-II enzymes (up to 107% for UDP-glucuronosyl-transferase, and up to 36% for glutathione S-transferase) were recorded only where the GLs to ITCs conversion had occurred. A boosting effect on catalase (up to 38%), NAD(P)H:quinone reductase (up to 70%), glutathione reductase and glutathione peroxidase (up to 10%) was also recorded, suggesting an indirect antioxidant capacity of the extracts. Overall, the general phase-I inhibition, together with the up-regulation of detoxifying phase-II and antioxidant enzymes, exerted by the TBCSE supplementation, seem to be in line with the classical chemopreventive theory, but whether the addition of exogenous MYR is relevant, still remains to be clarified. These results are in support of the potential health-promoting application of TBCSE, as a nutraceutical.

Black cabbage seed extract affects rat Cyp-mediated biotransformation: organ and sex related differences

Brassicaceae are widely consumed in many parts of the world and their dietary intake has been associated with cancer risk reduction. Extracts and metabolites derived from cruciferous vegetables have thus gained popularity as potential cancer chemopreventive agents. We have previously found, unexpectly, that glucoraphanin, the most extensively present glucosinolate in these vegetables, is a potent mutagen bioactivating Phase-I enzyme inducer. In the present study, the influence of black cabbage seed extract, rich in glucoraphanin, was investigated on Phase-I enzymes in different organs of male or female rats. Oral seed extract injection at 120 or 240 mg/kg b.w. for one or four consecutive days, significantly affected various cytochrome P450 (CYP) -linked monooxygenases in a complex way being the lung the most responsive organ (in males, up to ∼2600% increase for CYP2B1/2 isoform and ∼96% loss for CYP1A1, CYP3A1/2). These findings indicate that the extract may strongly enhance and/or suppress rat xenobiotic biotransformation pathways and that caution should be paid to the possible influence on human metabolism. These data suggest an overall evaluation of the balance between beneficial vs. possible adverse effects for each agent, even if of natural origin, prior to routinely, preventive mass use.

Modulation of cytochrome P450 and induction of DNA damage in Cyprinus carpio exposed in situ to surface water treated with chlorine or alternative disinfectants in different seasons

Epidemiological studies have shown an association between consumption of disinfected drinking water and adverse health outcomes. The chemicals used to disinfect water react with occurring organic matter and anthropogenic contaminants in the source water, resulting in the formation of disinfection by-products (DBPs). The observations that some DBPs are carcinogenic in animal models have raised public concern over the possible adverse health effects for humans. Here, the modulation of liver cytochrome P450-linked monooxygenases (MFO) and the genotoxic effects in erythrocytes of Cyprinus carpio fish exposed in situ to surface drinking water in the presence of disinfectants, such as sodium hypochlorite (NaClO), chlorine dioxide (ClO(2)) and peracetic acid (PAA), were investigated in winter and summer. A complex induction/suppression pattern of CYP-associated MFOs in winter was observed for all disinfectants. For example, a 3.4- to 15-fold increase was recorded of the CYP2B1/2-linked dealkylation of penthoxyresorufin with NaClO (10 days) and PAA (20 days). In contrast, ClO(2) generated the most notable inactivation, the CYP2E1-supported hydroxylation of p-nitrophenol being decreased up to 71% after 10 days' treatment. In summer, the degree of modulation was modest, with the exception of CYP3A1/2 and CYP1A1 supported MFOs (62% loss after 20 days PAA). The micronucleus (MN) induction in fish circulating erythrocytes was also analysed as an endpoint of genotoxic potential in the same fish population. Significant increases of MN induction were detected at the latest sampling time on fish exposed to surface water treated with chlorinate-disinfectants, both in winter (NaClO) and summer (NaClO and ClO(2)), while no effect was observed in fish exposed to PAA-treated water. These results show that water disinfection may be responsible for harmful outcomes in terms of MFO perturbation and DNA damage; if extrapolated to humans, they ultimately offer a possible rationale for the increased urinary cancer risk recorded in regular drinking water consumers.