FDA Approval Summary: Dabrafenib in Combination with Trametinib for BRAFV600E Mutation-Positive Low-Grade Glioma.

On March 16, 2023, the FDA approved dabrafenib in combination with trametinib (Tafinlar, Mekinist; Novartis Pharmaceuticals Corporation) for the treatment of pediatric patients with low-grade glioma (LGG) with a BRAFV600E mutation who require systemic therapy. FDA also approved oral formulations of both drugs suitable for patients who cannot swallow pills. This approval was based on the LGG cohort from study CDRB436G2201 (NCT02684058), a multicenter, open-label trial in which pediatric patients with LGG with a BRAFV600E mutation were randomly assigned 2:1 to dabrafenib plus trametinib (D+T) or carboplatin plus vincristine (C+V). The overall response rate (ORR) by independent review based on Response Assessment in Neuro-oncology LGG (2017) criteria was assessed in 110 patients randomly assigned to D+T (n = 73) or C+V (n = 37). ORR was 47% [95% confidence interval (CI), 35-59] in the D+T arm and 11% (95% CI, 3.0-25) in the C+V arm. Duration of response (DOR) was 23.7 months (95% CI, 14.5-NE) in the D+T arm and not estimable (95% CI, 6.6- NE) in the C+V arm. Progression-free survival (PFS) was 20.1 months (95% CI: 12.8, NE) and 7.4 months (95% CI, 3.6- 11.8) [HR, 0.31 (95% CI, 0.17-0.55); P < 0.001] in the D+T and C+V arms, respectively. The most common (>20%) adverse reactions were pyrexia, rash, headache, vomiting, musculoskeletal pain, fatigue, diarrhea, dry skin, nausea, hemorrhage, abdominal pain, and dermatitis acneiform. This represents the first FDA approval of a systemic therapy for the first-line treatment of pediatric patients with LGG with a BRAFV600E mutation.

Regulatory utility of physiologically-based pharmacokinetic modeling to support alternative bioequivalence approaches and risk assessment: A workshop summary report.

This report summarizes the proceedings for day 2 sessions 1 and 3 of the 2-day public workshop entitled "Regulatory Utility of Mechanistic Modeling to Support Alternative Bioequivalence Approaches," a jointly sponsored workshop by the US Food and Drug Administration (FDA) and the Center for Research on Complex Generics (CRCG). The aims of this workshop were: (1) to discuss how mechanistic modeling, including physiologically-based pharmacokinetic (PBPK) modeling and simulation, can support product development, and regulatory submissions; (2) to share the current state of mechanistic modeling for bioequivalence (BE) assessment through case studies; (3) to establish a consensus on best practices for using PBPK modeling for BE assessment to help drive further investment by the generic drug industry into mechanistic modeling and simulation; and (4) to introduce the concept of a Model Master File to improve model-sharing. The theme of day 2 covered PBPK absorption model for oral products as an alternative BE approach and a tool for supporting risk assessment and biowaiver (session 1), oral PBPK for evaluating the impact of food on BE (session 2), successful cases, and challenges for oral PBPK (session 3). This report summarizes the topics of the presentations of day 2 sessions 1 and session 3 from FDA, academia, and pharmaceutical industry, including the current status of oral PBPK, case examples as well as the challenges and opportunities in this area. In addition, panel discussions on the utility of oral PBPK in both new drugs and generic drugs from regulatory and industry perspective are also summarized.

Nanoparticles and the immune system.

Today nanotechnology is finding growing applications in industry, biology, and medicine. The clear benefits of using nanosized products in various biological and medical applications are often challenged by concerns about the lack of adequate data regarding their toxicity. One area of interest involves the interactions between nanoparticles and the components of the immune system. Nanoparticles can be engineered to either avoid immune system recognition or specifically inhibit or enhance the immune responses. We review herein reported observations on nanoparticle-mediated immunostimulation and immunosuppression, focusing on possible theories regarding how manipulation of particle physicochemical properties can influence their interaction with immune cells to attain desirable immunomodulation and avoid undesirable immunotoxicity.

Regulatory perspective on the importance of ADME assessment of nanoscale material containing drugs.

The promise of nanoscale material containing drug products to treat complex diseases is mounting. According to the literature, in addition to the liposomes, micelles, emulsions, there are novel drug delivery systems such as dendrimers and metal colloids at different stages of pre-clinical and clinical development. With the anticipation that more nanoscale material containing drug products will be submitted to the Food and Drug Administration (FDA) for approval in the future, FDA formed a Nanotechnology Task Force in 2006 to determine the critical regulatory issues regarding nanomaterials. As a result, all centers within the FDA are considering the development of guidance documents to address nanomaterial specific issues. It is well established in the literature that physico-chemical characterization (PCC) studies are crucial for nanomaterial containing drug products. However, this paper addresses the equally important topic of Absorption, Distribution, Metabolism and Excretion (ADME) studies for nanomaterials and provides examples of how physical properties affect biodistribution (i.e. the state of agglomeration, or aggregation, surface characteristics, stability of PEG). This paper also attempts to highlight some of the ADME study design issues related to nanomaterials such as the need for conducting biodistribution studies on each moiety of the multifunctional nanoparticles, dual labeled pharmacokinetic (PK) studies, and comparative PK studies on the free versus encapsulated drugs. In addition, this paper underlines the importance of long-term biodistribution and mass balance studies to understand the nanoparticle accumulation profile which may help to assess the safety and efficacy of the nanomaterial containing drug products. This review also lists some of the pre-clinical guidance documents that may help sponsors get started in developing data for inclusion in an initial investigational new drug application package for nanoscale material containing drug products.

Induction of autophagy in porcine kidney cells by quantum dots: a common cellular response to nanomaterials?

Quantum dots (QDs) are being investigated as novel in vivo imaging agents. The leaching of toxic metals from these QDs in biological systems is of great concern. This study compared the cytotoxic mechanisms of two QD species made of different core materials (cadmium selenide [CdSe] vs. indium gallium phosphide [InGaP]) but similar core sizes (5.1 vs. 3.7 nm) and surface compositions (both ZnS capped, lipid-coated and pegylated). The CdSe QD was found to be 10-fold more toxic to porcine renal proximal tubule cells (LLC-PK1) than the InGaP QD on a molar basis, as determined by MTT assay (48 h IC(50) 10nM for CdSe vs. 100nM for InGaP). Neither of the QD species induced appreciable oxidative stress, as determined by lipid peroxide and reduced glutathione content, suggesting that toxicity was not metal associated. In agreement, treatment of cells with CdSe QDs was not associated with changes in metallothionein-IA (MT-IA) gene expression or Cd-associated caspase 3 enzyme activation. By contrast, incubation of the LLC-PK1 cells with the InGaP QD resulted in a dramatic increase in MT-IA expression by 21- and 43-fold, at 8 and 24 h, respectively. The most remarkable finding was evidence of extensive autophagy in QD-treated cells, as determined by Lysotracker Red dye uptake, TEM, and LC3 immunobloting. Autophagy induction has also been described for other nanomaterials and may represent a common cellular response. These data suggest that QD cytotoxicity is dependent upon properties of the particle as a whole, and not exclusively the metal core materials.

Rapid distribution of liposomal short-chain ceramide in vitro and in vivo.

Ceramide, an endogenous sphingolipid, has demonstrated antieoplastic activity in vitro and in vivo. However, the chemotherapeutic utility of ceramide is limited because of its insolubility. To increase the solubility of ceramide, liposomal delivery systems have been used. The objective of the present study was to characterize the pharmacokinetics and tissue distribution of C6-ceramide and control (non-C6-ceramide) nanoliposomes in rats, using [14C]C6-ceramide and [3H]distearylphosphatidylcholine (DSPC) as tracers of the ceramide and liposome components, respectively. Ceramide liposomes were administered at 50 mg of liposomes/kg by jugular vein to female Sprague-Dawley rats. The apparent volume of distribution (Vd) of [3H]DSPC was approximately 50 ml/kg, suggesting that the liposomes were confined to the systemic circulation. In contrast, the Vd of [14C]C6-ceramide was 20-fold greater than that of liposomes, indicating extensive tissue distribution. This high Vd of [14C]C6-ceramide in relation to that of [3H]DSPC suggests that ceramide and liposomes distribute independently of each other. This disparate disposition was confirmed by tissue distribution studies, in which [14C]C6-ceramide exhibited rapid tissue accumulation compared with to [3H]DSPC. Examination of ceramide liposome blood compartmentalization in vitro also demonstrated divergent partitioning, with liposomes being confined to the plasma fraction and ceramide rapidly equilibrating between red blood cell and plasma fractions. A bilayer exchange mechanism for ceramide transfer is proposed to explain the results of the present study, as well as give insight into the documented antineoplastic efficacy of short-chain ceramide liposomes. Our studies suggest that this nanoscale PEGylated drug delivery system for short-chain ceramide offers rapid tissue distribution without adverse effects for a neoplastic-selective, insoluble agent.

In situ fiber optic method for long-term in vitro release testing of microspheres.

The objective of this study was to develop an in vitro release method for relatively unstable drugs in long-term modified release (MR) formulations, such as microspheres. Drug stability in the release medium can complicate in vitro release testing of such delivery systems. To overcome this problem, a method has been developed where the model drug, cefazolin, and its degradation products are monitored simultaneously, using UV fiber optic probes, to account for cumulative drug release from poly(lactic-co-glycolic) acid (PLGA) microspheres. United States Pharmacopeia (USP) Apparatus 2 and 4 were used to evaluate cefazolin release throughout the 30-day study period. Cefazolin exhibits an isosbestic point (wavelength where the drug and the degradation products have the same absorbance). Cumulative drug release was compared at the isosbestic (288 nm) point and at the UV max (270 nm). Monitoring at the isosbestic point allowed determination of total drug release with approximately 100% release by day 25. Whereas, at the UV max approximately 61% release was detected by day 25 as a result of drug degradation. Problems were encountered using USP Apparatus 2 with the in situ UV fiber optic probes as a result of microsphere accumulation at and interference with the probe detection window.

Evaluation of in vivo-in vitro release of dexamethasone from PLGA microspheres.

Two poly(lactic-co-glycolic acid) (PLGA) microsphere formulations, with different polymer molecular weights were investigated to determine whether an in vitro and in vivo relationship could be established for dexamethasone release. A USP apparatus 4 was used for in vitro testing. The in vivo release kinetics and pharmacodynamic effects of dexamethasone were evaluated using a Sprague Dawley rat model. The in vitro release from both formulations followed the typical triphasic profile of PLGA microspheres (initial burst release, followed by a lag phase and a secondary zero-order phase). The in vivo release profiles differed in that the lag phase was not observed and drug release rates were faster compared to the in vitro studies. It is speculated that the lack of lag phase in vivo may be a result of different PLGA degradation mechanisms in vivo as a consequence of the presence of enzymes as well as other in vivo factors such as interstitial fluid volume, and local pH. This may result in degradation of the PLGA microspheres proceeding from the surface inward in vivo. Whereas, in vitro an "inside out" degradation is thought to occur in some PLGA microsphere systems as a result of the autocatalytic degradation process where build up of acidic oligomeric units can occur within the microspheres. A linear in vitro-in vivo relationship was established after normalization of the time required to reach plateau for the in vitro and in vivo data and the in vitro release data were predictive of the in vivo release. Inflammation was significantly reduced in the tissue surrounding the dexamethasone microspheres compared to the positive control (empty microspheres) and the number of inflammatory cells was similar to that of normal tissue within one to three days.

Effect of acidic pH on PLGA microsphere degradation and release.

Polymer degradation and drug release kinetics from PLGA microspheres were investigated under neutral and acidic pH conditions. Two different Mw formulations (Mw: 25,000 and 70,000) were investigated and both exhibited a triphasic release profile at pH 7.4 as well as at pH 2.4. The initial burst and lag phases were similar for both pH values, while the secondary apparent-zero-order phase was substantially accelerated at pH 2.4. The polymer molecular weight change with time for the microspheres followed first order degradation kinetics for both pH values. A linear relationship was established between % drug release (post burst release) and Ln (Mw) for both pH conditions. Most significantly, morphological studies showed that the mechanism of polymer degradation changed from "inside-out" degradation at pH 7.4 to "outside-in" at pH 2.4. At pH 7.4, the microspheres followed the usual morphological changes such as surface pitting and pore formation. Whereas, at pH 2.4 the microspheres maintained smooth surfaces throughout the degradation process and were susceptible to fracturing. The fracturing of the microspheres was attributed to crystallization of oligomeric degradation products as a consequence of their low solubility at this pH. It also appeared that degradation occurred in a more homogeneous pattern at pH 2.4 than is typical of PLGA microspheres at pH 7.4. This may be a result of the entire microspheres experiencing a close-to-uniform pH at 2.4. However, at pH 7.4, the local micro-environmental pH within the microspheres has been reported to vary considerably due to a build up of acid oligomers. This heterogeneous degradation results in the random formation of channels within microspheres degraded at pH 7.4 which was not observed in those degraded at pH 2.4. This is the first time that morphological changes during PLGA microsphere degradation have been compared for low and neutral pH and the data shows a change in the mechanism of degradation at the low pH.

Elevated temperature accelerated release testing of PLGA microspheres.

Drug release from four different poly(lactic-co-glycolic) acid (PLGA) microsphere formulations was evaluated under "real-time" (37 degrees C) and accelerated release testing conditions of elevated temperature (45, 53, 60 and 70 degrees C) and increase in flow rate (4-35 ml/min) using United States Pharmacopeia (USP) apparatus 4. Formulation 5 K (composed of low Mw PLGA) exhibited diffusion-controlled kinetics in "real-time". Whereas, formulations 25 K, 28 K and 70 K (composed of medium and high Mw PLGA) followed erosion-controlled kinetics at 37 degrees C. Temperature-induced degradation of the microspheres was studied by monitoring drug release rates, change in molecular weight and morphological changes. Drug release rates at elevated temperature were used to predict "real-time" release applying the Arrhenius equation. The energy of activation for dexamethasone release from PLGA microspheres was calculated as 19.14 kcal/mol. Molecular weight change measured by gel permeation chromatography followed first order kinetics for both "real-time" and accelerated release. All four formulations exhibited morphological changes (such as surface pore closing and geometry change) at elevated temperature with consequent reduction in burst release.