KLRF1, a novel marker of CD56bright NK cells, predicts improved survival for patients with locally advanced bladder cancer.

BACKGROUND: Bladder tumor-infiltrating CD56bright NK cells are more tumor cytotoxic than their CD56dim counterparts. Identification of NK cell subsets is labor-intensive and has limited utility in the clinical setting. Here, we sought to identify a surrogate marker of bladder CD56bright NK cells and to test its prognostic significance. METHODS: CD56bright and CD56dim NK cells were characterized with the multiparametric flow (n = 20) and mass cytometry (n = 21) in human bladder tumors. Transcriptome data from bladder tumors (n = 351) profiled by The Cancer Genome Atlas (TCGA) were analyzed. The expression levels of individual markers in intratumoral CD56bright and CD56dim NK cells were visualized in tSNE plots. Expressions of activation markers were also compared between Killer Cell Lectin-Like Receptor Subfamily F Member 1 (KLRF1)+ and KLRF1- NK cells. RESULTS: Intratumoral CD56bright NK cells displayed a more activated phenotype compared to the CD56dim subset. Multiple intratumoral cell types expressed CD56, including bladder tumor cells and nonspecific intratumoral CD56 expression was associated with worse patient survival. Thus, an alternative to CD56 as a marker of CD56bright NK cells was sought. The activation receptor KLRF1 was significantly increased on CD56bright but not on CD56dim NK cells. Intratumoral KLRF1+ NK cells were more activated and expressed higher levels of activation molecules compared with KLRF1- NK cells, analogous to the distinct effector function of NK cells across CD56 expression. High intratumoral KLRF1 was associated with improved recurrence-free survival (hazard ratio [HR] 0.53, p = 0.01), cancer-specific survival (HR 0.47, p = 0.02), and overall survival (HR 0.54, p = 0.02) on multivariable analyses that adjusted for clinical and pathologic variables. CONCLUSIONS: KLRF1 is a promising prognostic marker in bladder cancer and may guide treatment decisions upon validation.

RNA sequencing in a penile cancer cohort: an investigation of biomarkers of cisplatin resistance and potential therapeutic drug targets.

OBJECTIVE: Chemoresistance in distant micrometastatic lesions may account for diminished durable response rates in advanced penile cancer. However, there are limited studies on new therapeutic targets and the identification of biomarkers that predict chemotherapy response in this population. Thus, we examine the expression of candidate biomarkers of cisplatin resistance, ERCC1 and E2F1, and perform next-generation sequencing on the cancer transcriptome in a penile cancer cohort. MATERIALS AND METHODS: In this retrospective cohort study, we identified 71 patients treated for penile squamous cell carcinoma between 2009 and 2019. Immunohistochemistry staining for ERCC1 and E2F1 was performed. H-scores were measured for patient specimens obtained from adjacent normal skin, primary tumor and metastatic lymph node specimens and correlated with RNA expression data obtained through next-generation sequencing. RESULTS: Of the 71 patients identified, 51 and 8 had available surgical specimens for immunohistochemistry and RNA sequencing, respectively. Median H-scores for ERCC1 in adjacent normal skin, primary and metastatic tumors were 17.04, 3.15, and 7.9 respectively compared to E2F1 (43.95, 15.54, 7.9). The median H-score for E2F1 was higher in poorly differentiated primary tumors (24.86) compared to well (7.62) and moderately differentiated (9.55, p = 0.055). Next generation sequencing showed no difference in RNA expression of E2F1 nor ERCC1 between primary tumors and metastatic lesions however did demonstrate elevated RNA expression of genes such as MMP1, and MMP10 in primary tumors compared to adjacent normal skin. CONCLUSION: We identify potential drug targets for metastatic penile cancer through next-generation RNA sequencing.

Corrigendum: Efficient decellularization of whole porcine kidneys improves reseeded cell behavior (2016 Biomed. Mater. 11 025003).

The manuscript 'Efficient decellularization of whole porcine kidneys improves reseeded cell behavior' (Poornejad et al 2016 Biomedical Materials 11: 025003) describes our efforts to improve the process for recellularization of porcine kidneys. We obtained what we believed to be an immortalized cell line of human renal cortical tubular epithelium (RCTE) cells from the Feinberg School of Medicine, Northwestern University to conduct our reseeding experiments. The RCTE cells that were provided to us were later discovered to actually be Madin-Darby Canine Kidney (MDCK) epithelial cells. A published erratum pertaining to this issue has been published (Caralt et al 2017 American Journal of Transplantation 17: 1429). Despite being of canine origin, MDCK cells are a distal tubule epithelial cell line that behave similarly to human RCTE cells. The conclusions regarding reseeding as reported in our paper are still sound.

Propensity matched comparative analysis of survival following chemoradiation or radical cystectomy for muscle-invasive bladder cancer.

OBJECTIVE: To compare survival outcome between chemoradiation therapy (CRT) and radical cystectomy (RC) for muscle-invasive bladder cancer (MIBC). PATIENTS AND METHODS: We conducted a retrospective analysis of patients with MIBC (≥cT2, N0, M0) in the National Cancer Database (2004-2013). CRT was defined as a radiation dose of ≥40 Gy and chemotherapy within 90 days of radiation. Descriptive statistics were used to compare groups. RC and CRT patients were propensity matched. Kaplan-Meier analysis was used to compare overall survival (OS). Multivariable Cox regression was used to determine predictors of survival. RESULTS: In all, 8 379 (6 606 RC and 1 773 CRT) patients met the inclusion criteria and 1 683 patients in each group were propensity matched. On multivariable extended Cox analysis, significant predictors of decreased OS were age, Charlson-Deyo Comorbidity score of 1, Charlson-Deyo Comorbidity score of 2, stage cT3-4, and urothelial histology. CRT was associated with decreased mortality at year 1 (hazard ratio [HR] 0.84, 95% confidence interval [CI] 0.74-0.96; P = 0.01), but at 2 years (HR 1.4, 95% CI 1.2-1.6; P < 0.001) and 3 years onward (HR 1.5, 95% CI 1.2-1.8; P < 0.001) CRT was associated with increased mortality. The 5-year OS was greater for RC than for CRT (38% vs 30%, P = 0.004). CONCLUSIONS: Initially after treatment for MIBC the risk of mortality is lower with CRT compared to RC. However, at ≥2 years after treatment the mortality risk favours RC. Patients who are suitable surgical candidates, with a low risk of morbidity, may be better served by RC.

Combined Partial Penectomy With Bilateral Robotic Inguinal Lymphadenectomy Using Near-infrared Fluorescence Guidance.

OBJECTIVE: To describe our novel technique for performing a combined partial penectomy and bilateral robotic inguinal lymphadenectomy using intraoperative near-infrared (NIR) fluorescence guidance with indocyanine green (ICG) and the DaVinci Firefly camera system. METHODS: A 58-year-old man presented status post recent excisional biopsy of a 2-cm lesion on the left coronal aspect of the glans penis. Pathology revealed "invasive squamous cell carcinoma of the penis with multifocal positive margins." His examination was suspicious for cT2 primary and his inguinal nodes were cN0. He was counseled to undergo partial penectomy with possible combined vs staged bilateral robotic inguinal lymphadenectomy. Preoperative computed tomography scan was negative for pathologic lymphadenopathy. Before incision, 5 mL of ICG was injected subcutaneously beneath the tumor. Bilateral thigh pockets were then developed simultaneously and a right, then left robotic modified inguinal lymphadenectomy was performed using NIR fluorescence guidance via the DaVinci Firefly camera. A partial penectomy was then performed in the standard fashion. RESULTS: The combined procedure was performed successfully without complication. Total operative time was 379 minutes and total robotic console time was 95 minutes for the right and 58 minutes to the left. Estimated blood loss on the right and left were 15 and 25 mL, respectively. A total of 24 lymph nodes were retrieved. CONCLUSION: This video demonstrates a safe and feasible approach for combined partial penectomy and bilateral inguinal lymphadenectomy with NIR guidance using ICG and the DaVinci Firefly camera system. The combined robotic approach has minimal morbidity and avoids the need for a staged procedure. Furthermore, use of NIR guidance with ICG during robotic inguinal lymphadenectomy is feasible and may help identify sentinel lymph nodes and improve the quality of dissection. Further studies are needed to confirm the utility of NIR guidance for robotic sentinel lymph node dissection.

Comparison of readmission and short-term mortality rates between different types of urinary diversion in patients undergoing radical cystectomy.

PURPOSE: To analyze the impact of urinary diversion type following radical cystectomy (RC) on readmission and short-term mortality rates. METHODS: Patients who underwent RC for bladder cancer in the National Cancer Data Base were grouped based on the type of urinary diversion performed: non-continent [ileal conduit (IC)] or two continent techniques [continent pouch (CP) and orthotopic neobladder (NB)]. We used propensity score matching and multivariable logistic regression models to compare 30-day readmission and 30- and 90-day mortality between the different types of urinary diversion. RESULTS: Among 11,933 patients who underwent RC, we identified 10,197 (85.5%) IC, 1044 (8.7%) CP, and 692 (5.8%) NB. Patients who received IC were significantly older and had more comorbidities (p < 0.0001). Continent diversions were more likely to be performed at an academic center (p < 0.0001). Surgery performed at a non-academic center was an independent predictor of 30-day readmission (OR 1.19, p = 0.010) and 30-day mortality (OR 1.27, p = 0.043). Patients undergoing NB had an increased likelihood of being readmitted (OR 1.41, p = 0.010). There was no significant difference in short-term mortality between groups. CONCLUSIONS: Patients undergoing NB had marginally increased rates of readmission compared to IC. Surgery performed at a non-academic center was associated with higher readmission and 30-day mortality. Similar short-term mortality rates were observed among the different types of urinary diversion.

Using Environment-Sensitive Fluorescent Probes to Characterize Liquid-Liquid Phase Separation in Supersaturated Solutions of Poorly Water Soluble Compounds.

PURPOSE: Highly supersaturated aqueous solutions of poorly soluble compounds can undergo liquid-liquid phase separation (LLPS) when the concentration exceeds the "amorphous solubility". This phenomenon has been widely observed during high throughput screening of new molecular entities as well as during the dissolution of amorphous solid dispersions. In this study, we have evaluated the use of environment-sensitive fluorescence probes to investigate the formation and properties of the non-crystalline drug-rich aggregates formed in aqueous solutions as a result of LLPS. METHODS: Six different environment-sensitive fluorophores were employed to study LLPS in highly supersaturated solutions of several model compounds, all dihydropyridine derivatives. RESULTS: Each fluoroprobe exhibited a large hypsochromic shift with decreasing environment polarity. Upon drug aggregate formation, the probes partitioned into the drug-rich phase and exhibited changes in emission wavelength and intensity consistent with sensing a lower polarity environment. The LLPS onset concentrations determined using the fluorescence measurements were in good agreement with light scattering measurements as well as theoretically estimated amorphous solubility values. CONCLUSIONS: Environment-sensitive fluorescence probes are useful to help understand the phase behavior of highly supersaturated aqueous solutions, which in turn is important in the context of developing enabling formulations for poorly soluble compounds.

Impact of Solubilizing Additives on Supersaturation and Membrane Transport of Drugs.

PURPOSE: Many enabling formulations give rise to supersaturated solutions wherein the solute possesses higher thermodynamic activity gradients than the solute in a saturated solution. Since flux across a membrane is driven by solute activity rather than concentration, understanding how solute thermodynamic activity varies with solution composition, particularly in the presence of solubilizing additives, is important in the context of passive absorption. METHODS: In this study, a side-by-side diffusion cell was used to evaluate solute flux for solutions of nifedipine and felodipine in the absence and presence of different solubilizing additives at various solute concentrations. RESULTS: At a given solute concentration above the equilibrium solubility, it was observed that the solubilizing additives could reduce the membrane flux, indicating that the extent of supersaturation can be reduced. However, the flux could be increased back to the same maximum value (which was determined by the concentration where liquid-liquid phase separation (LLPS) occurred) by increasing the total solute concentration. Qualitatively, the shape of the curves of solute flux through membrane as a function of total solute concentration is the same in the absence and presence of solubilizing additives. Quantitatively, however, LLPS occurs at higher solute concentrations in the presence of solubilizing additives. Moreover, the ratios of the LLPS onset concentration and equilibrium solubility vary significantly in the absence and presence of additives. CONCLUSIONS: These findings clearly point out the flaws in using solute concentration in estimating solute activity or supersaturation, and reaffirm the use of flux measurements to understand supersaturated systems. Clear differentiation between solubilization and supersaturation, as well as thorough understanding of their respective impacts on membrane transport kinetics is important for the rational design of enabling formulations for poorly soluble compounds.

Trends in the precipitation and crystallization behavior of supersaturated aqueous solutions of poorly water-soluble drugs assessed using synchrotron radiation.

Amorphous materials are high-energy solids that can potentially enhance the bioavailability of poorly soluble compounds. A major impediment to their widespread use as a formulation platform is the tendency of amorphous materials to crystallize. The aim of this study was to evaluate the relative crystallization tendency of six structural analogues belonging to the dihydropyridine class, in an aqueous environment in the absence and presence of polymers, using wide-angle X-ray scattering synchrotron radiation and polarized light microscopy. The crystallization behavior of precipitates generated from supersaturated solutions of the active pharmaceutical ingredients was found to be highly variable ranging from immediate to several hours in the absence of polymers. Polymers with intermediate hydrophilicity/hydrophobicity were found to substantially delay crystallization, whereas strongly hydrophilic or hydrophobic polymers were largely ineffective. Nuclear magnetic resonance spectroscopy experiments supported the supposition that polymers need to have affinity for both the drug-rich precipitate and the aqueous phase in order to be effective crystallization inhibitors. This study highlights the variability in the crystallization tendency of different compounds and provides insight into the mechanism of inhibition by polymeric additives.

Impact of polymers on the crystallization and phase transition kinetics of amorphous nifedipine during dissolution in aqueous media.

The commercial and clinical success of amorphous solid dispersions (ASD) in overcoming the low bioavailability of poorly soluble molecules has generated momentum among pharmaceutical scientists to advance the fundamental understanding of these complex systems. A major limitation of these formulations stems from the propensity of amorphous solids to crystallize upon exposure to aqueous media. This study was specifically focused on developing analytical techniques to evaluate the impact of polymers on the crystallization behavior during dissolution, which is critical in designing effective amorphous formulations. In the study, the crystallization and polymorphic conversions of a model compound, nifedipine, were explored in the absence and presence of polyvinylpyrrolidone (PVP), hydroxypropylmethyl cellulose (HPMC), and HPMC-acetate succinate (HPMC-AS). A combination of analytical approaches including Raman spectroscopy, polarized light microscopy, and chemometric techniques such as multivariate curve resolution (MCR) were used to evaluate the kinetics of crystallization and polymorphic transitions as well as to identify the primary route of crystallization, i.e., whether crystallization took place in the dissolving solid matrix or from the supersaturated solutions generated during dissolution. Pure amorphous nifedipine, when exposed to aqueous media, was found to crystallize rapidly from the amorphous matrix, even when polymers were present in the dissolution medium. Matrix crystallization was avoided when amorphous solid dispersions were prepared, however, crystallization from the solution phase was rapid. MCR was found to be an excellent data processing technique to deconvolute the complex phase transition behavior of nifedipine.

Enhancements and limits in drug membrane transport using supersaturated solutions of poorly water soluble drugs.

Amorphous solid dispersions (ASDs) give rise to supersaturated solutions (solution concentration greater than equilibrium crystalline solubility). We have recently found that supersaturating dosage forms can exhibit the phenomenon of liquid-liquid phase separation (LLPS). Thus, the high supersaturation generated by dissolving ASDs can lead to a two-phase system wherein one phase is an initially nanodimensioned and drug-rich phase and the other is a drug-lean continuous aqueous phase. Herein, the membrane transport of supersaturated solutions, at concentrations above and below the LLPS concentration has been evaluated using a side-by-side diffusion cell. Measurements of solution concentration with time in the receiver cell yield the flux, which reflects the solute thermodynamic activity in the donor cell. As the nominal concentration of solute in the donor cell increases, a linear increase in flux was observed up to the concentration where LLPS occurred. Thereafter, the flux remained essentially constant. Both nifedipine and felodipine solutions exhibit such behavior as long as crystallization is absent. This suggests that there is an upper limit in passive membrane transport that is dictated by the LLPS concentration. These results have several important implications for drug delivery, especially for poorly soluble compounds requiring enabling formulation technologies.

Prostate cancer and the increasing role of active surveillance.

Prostate cancer (PC) is the most often diagnosed non-skin cancer and the second leading cause of cancer-related death among men in the United States. As a result, for many years the American Urological Association (AUA) and the American Cancer Society have issued statements recommending screening for PC, resulting in its widespread implementation in the United States. Recently, the United States Preventative Services Task Force gave PC screening a recommendation of D, that is, against PC screening for all men. The AUA countered this recommendation, stating that since the development of PC screening using prostate-specific antigen, a reduction in PC-specific mortality has been seen, and that the risk reduction occurred in a setting in which many of the patients were not aggressively treated for prostate cancer. Active surveillance may be described as a method to potentially delay or obviate the need for treatment in men with clinically insignificant PC or PC thought to be at low risk for progression. Studies have shown no significant difference in outcome or pathology between men with low risk PC who receive treatment at the point of progression and those undergoing immediate treatment. Ongoing studies are evaluating the efficacy and utility of active surveillance for low-risk PC. Interim results of these studies have shown that approximately 30% of patients progress on active surveillance. However, "progression" does not necessarily mean treatment failure; rarely do patients develop locally advanced or metastatic disease. Active surveillance has also been shown to be cost-effective when compared with immediate treatment for PC. Longer follow-up may continue to show an increased benefit of active surveillance as a reasonable initial approach to the management of men with low-risk, clinically localized PC.

Impact of anatomical and socioeconomic factors on timing of urological consultation for boys with cryptorchidism.

PURPOSE: Cryptorchidism is a common finding in infants and young boys. Early repair lessens the extent of testicular injury. We hypothesized that anatomical and socioeconomic factors affect the timing of consultation and treatment for boys with cryptorchidism. MATERIALS AND METHODS: Under an institutional review board approved protocol we reviewed the records at a single institution of children who underwent exploration for unilateral or bilateral cryptorchidism. Demographic and anatomical factors were recorded. RESULTS: The median age of 677 boys at consultation and surgery was 20.3 and 28.9 months, respectively. Median age at consultation for boys with nonpalpable and palpable testicles was 12.3 and 20.9 months, respectively (p = 0.03). Boys with a concomitant penile anomaly had a younger median age at consultation than boys without a penile anomaly (8.5 vs 20.3 months, p <0.01). Demographic factors did not vary with respect to time to consultation and surgery (p >0.05). Multivariate analysis showed that abdominal site and concomitant penile anomaly were associated with earlier time to consultation (p = 0.02 and <0.01, respectively). CONCLUSIONS: The timing of consultation for boys with undescended testicles does not vary in regard to race, language or insurance type at this tertiary care institution. Instead, anatomical factors influenced age at consultation for boys with cryptorchidism. This suggests that in some geographic regions access to care is not restricted for minorities or noncommercially insured children.

Dissolution and precipitation behavior of amorphous solid dispersions.

Amorphous solid dispersions (ASDs) are widely utilized in the pharmaceutical industry for bioavailability enhancement of low solubility drugs. The important factors governing the dissolution behavior of these systems are still far from adequately understood. As a consequence, it is of interest to investigate the behavior of these systems during the dissolution process. The purpose of this research was twofold. First, the degree of supersaturation generated upon dissolution as a function of drug-polymer composition was investigated. Second, an investigation was conducted to correlate physical behavior upon dissolution with polymer loading. Felodipine and indomethacin were selected as model drugs and hydroxypropylmethylcellulose (HPMC) and polyvinylpyrrolidone (PVP) were used to form the dispersions. Diffusion and nuclear magnetic resonance spectroscopy experiments revealed that the extent of bulk supersaturation generated on dissolution of the ASD did not depend on the drug-polymer ratio. Interestingly, the maximum supersaturation generated was similar to the predicted amorphous solubility advantage. However, dynamic light scattering measurements revealed that particles on the submicron scale were generated during dissolution of the solid dispersions containing 90% polymer, whereas solid dispersions at a 50% polymer loading did not yield these nanoparticles. The nanoparticles were found to result in anomalous concentration measurements when using in situ ultraviolet spectroscopy. The supersaturation generated upon dissolution of the solid dispersions was maintained for biologically relevant timeframes for the HPMC dispersions, whereas PVP appeared to be a less effective crystallization inhibitor.

Influence of particle size on the ultraviolet spectrum of particulate-containing solutions: implications for in-situ concentration monitoring using UV/Vis fiber-optic probes.

PURPOSE: To critically evaluate the effect of submicron and micron-sized organic particulates on the ultraviolet (UV) absorption spectra of aqueous systems and assess the applicability of UV/Vis fiber-optic probes for in-situ concentration monitoring in the presence of particles of different sizes. METHODS: UV absorbance spectra were obtained for aqueous felodipine suspensions containing a range of particle sizes (300 nm-400 µm) and suspension concentrations and for methanolic solutions of different concentrations and amorphous films of different thicknesses. Select suspensions were further characterized using nuclear magnetic resonance (NMR) experiments. Mie theory was used to provide insight into the role of particle size on scattering and absorption of UV radiation. RESULTS: Large increases in absorbance as a function of total suspension concentration were observed for nanosuspensions but not for the other particle sizes evaluated. NMR measurements of solution concentration indicated that the observed increases in UV absorbance values for these systems were not caused by increases in the concentration of dissolved molecules, implying that nanoparticles of felodipine might absorb UV light. Mie theory-based calculations enabled reconstruction of the experimental observations and supported this hypothesis. CONCLUSIONS: For solutions containing small (submicron) felodipine particles, UV spectra were influenced by absorption of the particles and contributions from absorption of dissolved molecules and scattering of the particles. Caution should be applied when using in situ UV/VIS-probes to monitor the amount of dissolved material during dissolution, in particular when small particles are present (e.g. dissolution of nanoparticulate formulations) or generated (e.g. precipitation of supersaturated solutions) in the dissolution medium.

Ex-premature infant boys with hypospadias are similar in size to age-matched, ex-premature infant boys without hypospadias.

OBJECTIVE: Studies have postulated that hypospadias, prematurity, and low birth weight are linked by defects in androgen signaling. To determine whether premature, hypospadiac boys are small and remain so, we compared their size at birth and at hypospadias repair to premature boys who underwent post-neonatal circumcision. METHODS: We identified premature boys admitted to Texas Children's Hospital who underwent either hypospadias repair or circumcision after 4 months of age. Age, weight, and height at birth and surgery were recorded. RESULTS: Fifty-four boys had hypospadias and 34 did not. For hypospadiac boys, the mean birth weight and age, height, and weight at surgery were lower than for boys without hypospadias. More importantly, length-for-age and weight-for-age percentiles were also lower for hypospadiac boys. When subset analysis was performed on boys younger than 2 years at surgery, however, there were no significant differences in height or weight between hypospadiac and non-hypospadiac boys. CONCLUSION: Our series suggests that premature, hypospadiac boys are born smaller than age-matched, non-hypospadiac controls. However, there were no age-corrected size differences between hypospadiac and non-hypospadiac boys at surgery. This implies that hypospadiac boys exhibit post-neonatal 'rebound' growth. Global growth deficits, if any, do not persist in hypospadiac boys.

Understanding the behavior of amorphous pharmaceutical systems during dissolution.

PURPOSE: To investigate the underlying physical processes taking place during dissolution of amorphous pharmaceuticals and correlate them to the observed solution concentration-time profiles. Felodipine and indomethacin were used as model hydrophobic compounds. METHODS: Concentration-time profiles were monitored during dissolution of the model amorphous compounds using in situ fiber-optic ultraviolet spectroscopy. Crystallization of the solid exposed to an aqueous environment was monitored using Raman spectroscopy and/or powder X-ray diffraction. Polarized light microscopy was used to provide qualitative information about crystallization processes. RESULTS: For felodipine, a small extent of supersaturation was generated via dissolution at 25 degrees C but not at 37 degrees C. The amorphous solid was found to crystallize rapidly at both temperatures upon exposure to the dissolution medium. Addition of low concentrations of polymers to the dissolution medium was found to delay crystallization of the amorphous solid, leading to the generation of supersaturated solutions. Amorphous indomethacin did not crystallize as readily in an aqueous environment; hence, dissolution resulted in supersaturated solutions. However, crystallization from these supersaturated solutions was rapid. Polymeric additives were able to retard crystallization from supersaturated solutions of both indomethacin and felodipine for up to 4 h. CONCLUSIONS: The dissolution advantage of amorphous solids can be negated either by crystallization of the amorphous solid on contact with the dissolution medium or through rapid crystallization of the supersaturated solution. Polymeric additives can potentially retard both of these crystallization routes, leading to the generation of supersaturated solutions that can persist for biologically relevant timeframes.

Evaluation of drug-polymer miscibility in amorphous solid dispersion systems.

PURPOSE: To evaluate drug-polymer miscibility behavior in four different drug-polymer amorphous solid dispersion systems, namely felodipine-poly(vinyl pyrrolidone) (PVP), nifedipine-PVP, ketoconazole-PVP, and felodipine-poly(acrylic acid) (PAA). MATERIALS AND METHODS: Amorphous solid dispersion samples were prepared at different drug-to-polymer ratios and analyzed using differential scanning calorimetry (DSC), mid-infrared (IR) spectroscopy, and powder X-ray diffractometry (PXRD). To help with interpretation of the IR spectra, principal components (PC) analysis was performed. Pair Distribution Functions (PDFs) of the components in the dispersion were determined from the PXRD data, and the pure curves of the components were also extracted from PXRD data using the Pure Curve Resolution Method (PCRM) and compared against experimentally obtained results. RESULTS: Molecular-level mixing over the complete range of concentration was verified for nifedipine-PVP and felodipine-PVP. For felodipine-PAA, drug-polymer immiscibility was verified for samples containing 30 to 70% polymer, while IR results suggest at least some level of mixing for samples containing 10 and 90% polymer. For ketoconazole-PVP system, partial miscibility is suspected, whereby the presence of one-phase amorphous solid dispersion system could only be unambiguously verified at higher concentrations of polymer. CONCLUSIONS: The three techniques mentioned complement each other in establishing drug-polymer miscibility in amorphous solid dispersion systems. In particular, IR spectroscopy and PXRD are sensitive to changes in local chemical environments and local structure, which makes them especially useful in elucidating the nature of miscibility in binary mixtures when DSC results are inconclusive or variable.

Effect of polymer type on the dissolution profile of amorphous solid dispersions containing felodipine.

Amorphous solid dispersions are used as a strategy to improve the bioavailability of poorly water-soluble compounds. When formulating with a polymer, it is important not only for the polymer to stabilize against crystallization in the solid state, but also to improve the dissolution profile through inhibiting crystallization from the supersaturated solution generated by dissolution of the amorphous material. In this study, the dissolution profiles of solid dispersions of felodipine formulated with poly(vinylpyrrolidone) (PVP), hydroxypropyl methylcellulose (HPMC) or hydroxypropyl methylcellulose acetate succinate (HPMCAS) were compared. In addition, concentration versus time profiles were evaluated for the supersaturated solutions of felodipine in the presence and absence of the polymers. HPMCAS was found to maintain the highest level of supersaturation for the greatest length of time for both the dissolution and solution crystallization experiments, whereas PVP was found to be the least effective crystallization inhibitor. All polymers appeared to reduce the crystal growth rates of felodipine at an equivalent supersaturation and this mechanism most likely contributes to the enhanced solution concentration values observed during dissolution of the amorphous solid dispersions.