Phosphatidylcholine head group chemistry alters the extrahepatic accumulation of lipid-conjugated siRNA.

Small interfering RNAs (siRNAs) are revolutionizing the treatment of liver-associated indications. Yet, robust delivery to extrahepatic tissues remains a challenge. Conjugating lipids (e.g., docosanoic acid [DCA]) to siRNA supports extrahepatic delivery, but tissue accumulation remains lower than that achieved in liver by approved siRNA therapeutics. Early evidence suggests that functionalizing DCA with a head group (e.g., phosphatidylcholine [PC]) may enhance delivery to certain tissues. Here, we report the first systematic evaluation of the effect of PC head group chemistry on the extrahepatic distribution of DCA-conjugated siRNAs. We show that functionalizing DCA with a PC head group enhances siRNA accumulation in heart, muscle, lung, pancreas, duodenum, urinary bladder, and fat. Varying the size of the linker between the phosphate and choline moiety of the PC head group altered the extrahepatic accumulation of siRNA, with the optimal linker length being different for different tissues. Increasing PC head group valency also improved extrahepatic accumulation in a tissue-specific manner. This study demonstrates the structural impact of the PC moiety on the biodistribution of lipid-conjugated siRNA and introduces multiple novel PC variants for the chemical optimization of DCA-conjugated siRNA. These chemical variants can be used in the context of other lipids to increase the repertoire of conjugates for the extrahepatic distribution of siRNAs.

Dendritic amphiphilic siRNA: Selective albumin binding, in vivo efficacy, and low toxicity.

Although an increasing number of small interfering RNA (siRNA) therapies are reaching the market, the challenge of efficient extra-hepatic delivery continues to limit their full therapeutic potential. Drug delivery vehicles and hydrophobic conjugates are being used to overcome the delivery bottleneck. Previously, we reported a novel dendritic conjugate that can be appended efficiently to oligonucleotides, allowing them to bind albumin with nanomolar affinity. Here, we explore the ability of this novel albumin-binding conjugate to improve the delivery of siRNA in vivo. We demonstrate that the conjugate binds albumin exclusively in circulation and extravasates to various organs, enabling effective gene silencing. Notably, we show that the conjugate achieves a balance between hydrophobicity and safety, as it significantly reduces the side effects associated with siRNA interactions with blood components, which are commonly observed in some hydrophobically conjugated siRNAs. In addition, it reduces siRNA monocyte uptake, which may lead to cytokine/inflammatory responses. This work showcases the potential of using this dendritic conjugate as a selective albumin binding handle for the effective and safe delivery of nucleic acid therapeutics. We envision that these properties may pave the way for new opportunities to overcome delivery hurdles of oligonucleotides in future applications.

Divalent siRNAs are bioavailable in the lung and efficiently block SARS-CoV-2 infection.

The continuous evolution of SARS-CoV-2 variants complicates efforts to combat the ongoing pandemic, underscoring the need for a dynamic platform for the rapid development of pan-viral variant therapeutics. Oligonucleotide therapeutics are enhancing the treatment of numerous diseases with unprecedented potency, duration of effect, and safety. Through the systematic screening of hundreds of oligonucleotide sequences, we identified fully chemically stabilized siRNAs and ASOs that target regions of the SARS-CoV-2 genome conserved in all variants of concern, including delta and omicron. We successively evaluated candidates in cellular reporter assays, followed by viral inhibition in cell culture, with eventual testing of leads for in vivo antiviral activity in the lung. Previous attempts to deliver therapeutic oligonucleotides to the lung have met with only modest success. Here, we report the development of a platform for identifying and generating potent, chemically modified multimeric siRNAs bioavailable in the lung after local intranasal and intratracheal delivery. The optimized divalent siRNAs showed robust antiviral activity in human cells and mouse models of SARS-CoV-2 infection and represent a new paradigm for antiviral therapeutic development for current and future pandemics.

Duplicated extrahepatic bile duct (type Vb): An important rare anomaly.

Congenital duplication of the extrahepatic bile duct (DEBD) is an unusual anomaly of the biliary system. It occurs due to inability of the embryological duplex biliary system to regress. DEBD has various subtypes depending on the morphology and opening of the aberrant common bile duct. It can have distinct complications. We encountered a 38-year-old lady who experienced pain in the right upper abdomen along with a low-grade fever. Magnetic resonance cholangiopancreatography revealed DEBD with multiple calculi in the right hepatic duct (ductolithiasis) and joining of the right hepatic duct with the left hepatic duct in the intrapancreatic region. Endoscopic retrograde cholangiography failed to clear the calculi from the right duct. They were then managed by common bile duct exploration and roux-en-Y right hepaticojejunostomy for biliary drainage. Her postoperative period was uneventful. She is currently doing well after three months of follow-up. Hence, a proper preoperative delineation of such rare anomalies is essential. It could avoid inadvertent injury to the bile duct and operative complications.

Laparoscopic Witzel feeding jejunostomy: a procedure overlooked!

Purpose@#Feeding jejunostomy (FJ) is a critical procedure to establish a source of enteral nutrition for upper gastrointestinal disorders. Minimally invasive surgery has the inherent benefit of better patient outcomes, less postoperative pain, and early discharge. This study aims to describe our total laparoscopic technique of Witzel FJ and to compare its outcome with its open counterpart. @*Methods@#A retrospective database analysis was performed in patients who underwent laparoscopic (n = 20) and open (n = 21) FJ as a stand-alone procedure from July 2018 to July 2022. A readily available nasogastric tube (Ryles tube) and routine laparoscopic instruments were used to perform laparoscopic FJ. Perioperative data and postoperative outcomes were analyzed. @*Results@#Baseline preoperative variables were comparable in both groups. The median operative duration in the laparoscopic FJ group was 180 minutes vs. 60 minutes in the open FJ group (p = 0.01). Postoperative length of hospital stay was 3 days vs. 4 days in the laparoscopic and open FJ groups, respectively (p = 0.08). Four patients in the open FJ group suffered from an immediate postoperative complication (none in the laparoscopic FJ group). After a median follow-up of 10 months, fewer patients in the laparoscopic FJ group had complications such as tube clogging, tube dislodgement, surgical-site infection, and small bowel obstruction. @*Conclusion@#Laparoscopic FJ with the Witzel technique is a safe and feasible procedure with a comparable outcome to the open technique. Patient selection is vital to overcome the initial learning curve.

Chemical optimization of siRNA for safe and efficient silencing of placental sFLT1.

Preeclampsia (PE) is a rising, potentially lethal complication of pregnancy. PE is driven primarily by the overexpression of placental soluble fms-like tyrosine kinase 1 (sFLT1), a validated diagnostic and prognostic marker of the disease when normalized to placental growth factor (PlGF) levels. Injecting cholesterol-conjugated, fully modified, small interfering RNAs (siRNAs) targeting sFLT1 mRNA into pregnant mice or baboons reduces placental sFLT1 and ameliorates clinical signs of PE, providing a strong foundation for the development of a PE therapeutic. siRNA delivery, potency, and safety are dictated by conjugate chemistry, siRNA duplex structure, and chemical modification pattern. Here, we systematically evaluate these parameters and demonstrate that increasing 2'-O-methyl modifications and 5' chemical stabilization and using sequence-specific duplex asymmetry and a phosphocholine-docosanoic acid conjugate enhance placental accumulation, silencing efficiency and safety of sFLT1-targeting siRNAs. The optimization strategy here provides a framework for the chemical optimization of siRNAs for PE as well as other targets and clinical indications.

Mirizzi Syndrome With Bouveret Syndrome: A Rare Amalgam.

Mirizzi and Bouveret syndromes are uncommon but important complications of calculous cholecystitis. Mirizzi syndrome commonly presents with jaundice due to extrinsic compression on the common bile duct by an impacted stone at the gall bladder infundibulum, whereas Bouveret syndrome presents with gastric outlet obstruction due to a large stone in the duodenum. Our case is a 65-year-old lady who presented with pain in the right upper abdomen associated with nausea and vomiting. Contrast-enhanced computed tomography and MRI of the abdomen were suggestive of calculus in the infundibulum of the gall bladder with compression over the common bile duct and a large stone in the first part of the duodenum. Upper gastrointestinal endoscopy confirmed the findings but could not retrieve the stone. Cholecystectomy with the retrieval of calculus from the infundibulum and duodenum was performed with the closure of the fistulous opening. The patient did well in the post-operative period and is doing well after nine months of follow-up. Chronic calculus cholecystitis can present in varied forms, and one should be aware of such rare complications and their management.