An Improved Impact Ratio for Identifying Critical Process Parameters in Pharmaceutical Manufacturing Processes

The identification of critical process parameters in biologics and small molecule process development is a key element of quality by design. The objectivity and consistency of procedures to identify critical process parameters can be improved with the use of impact ratios. Impact ratios quantify a process parameter's practical effect on a critical quality attribute relative to the critical quality attribute's acceptance limits. If the impact ratio is large, i.e., exceeds a predefined impact ratio threshold, the recommendation is to classify the process parameter as a critical process parameter. This article introduces an improved and mathematically well-defined impact ratio. Benefits of this impact ratio are a consistent interpretation for many scenarios commonly encountered in practice, high suitability to automation, and the possibility of standardizing on a single impact ratio definition for pharmaceutical manufacturing.

Stereoselective Synthesis of the IDO Inhibitor Navoximod

A highly efficient asymmetric synthesis of the IDO inhibitor navoximod, featuring the stereoselective installation of two relative and two absolute stereocenters from an advanced racemic intermediate, is described. The stereocenters were set via a crystallization-induced dynamic resolution along with two selective ketone reductions: one via a biocatalytic ketoreductase transformation and one via substrate-controlled hydride delivery from LiAlH(Ot-Bu)₃. Following this strategy, navoximod was synthesized in 10 steps from 2-fluorobenzaldehyde and isolated in 23% overall yield with 99.7% ee and high purity.

Impact of the C1' configuration of abasic sites on DNA duplex structure

Naturally occurring abasic sites in DNA exist as an equilibrium mixture of the aldehyde, the hydrated aldehyde, and the hemiacetal forms (dominant). The influence of the configuration of the C1' hydroxyl group of the hemiacetal form on duplex structure and abasic site repair has been examined using novel carbocyclic analogues. Both the alpha- and beta-forms of this novel abasic site were introduced into oligomeric DNA using the standard DMT-phosphoramidite approach in an automated solid-phase synthesizer. Solution structures of the d(CGTACXCATGC).d(GCATGAGTACG) duplex (where X is the alpha- or beta-anomer of the carbocyclic abasic site analogue) were determined by NMR spectroscopy and restrained molecular dynamics simulations. The structures were only minimally perturbed by the presence of either anomer of the abasic site. All residues adopted an anti conformation, and Watson-Crick alignments were observed on all base pairs of the duplexes. At the lesion site, the abasic residues and their partner adenines showed increased dynamic behavior but adopted intrahelical positions in the final refined structures. Incision of duplexes having the alpha- or beta-anomer of the carbocyclic abasic site by human AP endonuclease showed that the enzyme recognizes both configurations of the lesion and nicks the DNA backbone with similar efficiency. Our results challenge the suggestion that Ape1 is stereoselective and imply a plasticity at the active site of the enzyme for accommodating either anomer of the lesion.

Rare case of left-sided ureteroduodenal fistula

BACKGROUND/AIMS

Ureteroduodenal fistulas are rare and only 11 cases have been reported in the literature since 1918. Diagnosis requires careful observation of symptoms.

METHODS

The case presented demonstrates a 68-year-old female with left-sided ureteroduodenal fistula confirmed by CT scan. A duodenal fistula was localized and an atrophic left kidney was identified and repaired.

RESULTS

Nephroureterectomy was performed and an omental patch was used for the repair. No complications were encountered during the postoperative course.

CONCLUSIONS

Recurrent chronic urinary tract infection, pyuria and hematuria can indicate this rare disease. Early testing and detection can improve the chances of renal preservation.

Signal transduction mediated by adhesion of human trabecular meshwork cells to extracellular matrix

In this study we investigated the signaling event induced by adhesion of human trabecular meshwork (TM) cells to extracellular matrix (ECM) elements such as fibronectin. The role of tyrosine phosphorylation in adhesion was evaluated. A number of intracellular entities involved in the adhesion-mediated pathways were identified. For the experiments, human TM cells were seeded onto fibronectin- or polylysine (negative control)-coated plates. Fifteen, 30, 90 and 240 min after the seeding, cell lysates were collected. Immunoblotting analysis revealed that tyrosine phosphorylation occurred within 15 min of adhesion of TM cells to fibronectin and the level increased with time. The phosphotyrosyl proteins had molecular masses 25-220 kDa. A much lower level of tyrosine phosphorylation was observed when cells were plated on polylysine. Immunoprecipitation experiments indicated that the phosphotyrosine-containing proteins included focal adhesion kinase, paxillin, phosphatidylinositol 3-kinase and mitogen activated protein kinase. Within 30 min of adherence to fibronectin, human TM cells immunostained for paxillin and phosphotyrosine and exhibited prominent focal contacts. When treated with tyrosine kinase inhibitors genistein and herbimycin A and a protein kinase C (PKC) pseudosubstrate peptide inhibitor, cell adhesion to fibronectin was compromised and focal contact formation was limited. These results demonstrated that in human TM cells, tyrosine kinase was activated upon their adherence to fibronectin. PKC also appeared to play a role in modulation of the cell-matrix adhesion process. The current study provides insight into the signaling pathways that are linked to the ECM-induced events in TM cells. Elucidation of the hierarchy of signal responses may help develop strategies manipulating the cell-matrix interactions in the TM system.

Use of chitosan in compressed tablets of diclofenac sodium: inhibition of drug release in an acidic environment

The purpose of this study was to evaluate the potential utility of chitosan (I) in inhibiting diclofenac sodium (II) release in the gastric environment from a directly compressible tablet formulation. I, subjected to depolymerization to improve its microcrystallinity and subsequent compressibility, was then used to prepare tablets of II. A full-factorial design was employed to evaluate the effects of degree of N-deacetylation of I, and the pH and ionic strengths, mu, of the dissolution media on drug release. Directly compressible tablets were prepared from admixtures of 25 mg of II, 174 mg of I of various degrees of N-deacetylation (74, 87, and 92%), and 1 mg of magnesium stearate. The in vitro dissolution studies were performed using aqueous buffers (pHs 1.2, 3.8, and 6.8, and mu of approximately 1.0 and 0.1). The slopes of logarithmically transformed cumulative percent released-time curves (from t = 0 to t = 5 hr) were compared. Analyses of variance performed using SAS indicated that the degree of N-deacetylation of chitosan significantly affected drug release at pHs 1.2 and 6.8 (p < 0.0001). An increase in the pH of the dissolution medium resulted in an increase in drug release (p < 0.0001). The ionic strength of the dissolution medium did not significantly affect drug release at any of the pHs studied (p > 0.198). Besides the poor aqueous solubility of II, the two factors possibly affecting the drug release in the acidic environment were (a) the formation of a rate-limiting chitosan gel barrier; and (b) the ionic interaction of II with ionized amino groups of I.