Property-Driven Design and Development of Lipids for Efficient Delivery of siRNA.

Ionizable cationic lipids are critical components involved in nanoparticle formulations, which are utilized in delivery platforms for RNA therapeutics. While general criteria regarding lipophilicity and measured pKa in formulation are understood to have impacts on utility in vivo, greater granularity with respect to the impacts of the structure on calculated and measured physicochemical parameters and the subsequent performance of those ionizable cationic lipids in in vivo studies would be beneficial. Herein, we describe structural alterations made within a lipid class exemplified by 4, which allow us to tune calculated and measured physicochemical parameters for improved performance, resulting in substantial improvements versus the state of the art at the outset of these studies, resulting in good in vivo activity within a range of measured basicity (pKa = 6.0-6.6) and lipophilicity (cLogD = 10-14).

Development of a Microfluidic-Based Post-Treatment Process for Size-Controlled Lipid Nanoparticles and Application to siRNA Delivery.

Microfluidic methodologies for preparation of lipid nanoparticles (LNPs) based on an organic solvent injection method enable precise size control of the LNPs. After preparation of LNPs, the organic solvent injection method needs some post-treatments, such as overnight dialysis or direct dilution with a buffer solution. LNP production using the microfluidic-based organic solvent injection method is dominated by kinetics rather than thermodynamics. Kinetics of ethanol removal from the inner and outer membranes of LNPs could induce a structural change in the membrane that could lead to fusion of LNPs. However, the effects of microfluidic post-treatment on the final size of LNPs have not been sufficiently understood. Herein, we investigated the effect of the post-treatment processes on the final product size of LNPs in detail. A simple baffle device and a model lipid system composed of a neutral phospholipid (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine, POPC) and cholesterol were used to produce the LNPs. We demonstrated that flow conditions of the post-treatment diluting the remaining ethanol in the LNP suspension affected the final product size of LNPs. Based on the findings, we developed an integrated baffle device composed of an LNP production region and a post-treatment region for a microfluidic-based LNP production system; this integrated baffle device prevented the undesirable aggregation or fusion of POPC LNPs even for the high-lipid-concentration condition. Finally, we applied our concept to small interfering RNA (siRNA) delivery and confirmed that no significant effects due to the continuous process occurred on the siRNA encapsulation efficiency, biological distribution, and knockdown activity. The microfluidic post-treatment method is expected to contribute to the production of LNPs for practical applications and the development of novel LNP-based nanomedicines.

Oxime Coupling of Active Site Inhibited Factor Seven with a Nonvolatile, Water-Soluble Fluorine-18 Labeled Aldehyde.

A nonvolatile fluorine-18 aldehyde prosthetic group was developed from [18F]SFB, and used for site-specific labeling of active site inhibited factor VII (FVIIai). FVIIai has a high affinity for tissue factor (TF), a transmembrane protein involved in angiogenesis, proliferation, cell migration, and survival of cancer cells. A hydroxylamine N-glycan modified FVIIai (FVIIai-ONH2) was used for oxime coupling with the aldehyde [18F]2 under mild and optimized conditions in an isolated RCY of 4.7 ± 0.9%, and a synthesis time of 267 ± 5 min (from EOB). Retained binding and specificity of the resulting [18F]FVIIai to TF was shown in vitro. TF-expression imaging capability was evaluated by in vivo PET/CT imaging in a pancreatic human xenograft cancer mouse model. The conjugate showed exceptional stability in plasma (>95% at 4 h) and a binding fraction of 90%. In vivo PET/CT imaging showed a mean tumor uptake of 3.8 ± 0.2% ID/g at 4 h post-injection, a comparable uptake in liver and kidneys, and low uptake in normal tissues. In conclusion, FVIIai was labeled with fluorine-18 at the N-glycan chain without affecting TF binding. In vitro specificity and a good in vivo imaging contrast at 4 h postinjection was demonstrated.

Inhibitor development in patients with congenital factor VII deficiency, a study on 50 Iranian patients.

: Congenital factor VII (FVII) deficiency is a rare bleeding disorder with an estimated prevalence of 1 per 500 000 in the general population. On-demand replacement therapy is the main therapeutic choice in patients with congenital FVII deficiency. Inhibitor formation against exogenous FVII is very rare and can cause challenges in the management of the disorder. The present study was conducted to assess the prevalence of FVII inhibitor in 50 patients with congenital FVII deficiency under on-demand or prophylaxis treatment by recombinant activated FVII. All patients with confirmed congenital FVII deficiency were assessed for inhibitor development in regular intervals. Inhibitor titer was determined by a modified Nijmegen-Bethesda assay. The study results were analyzed by SPSS software. Among all cases, two patients (4%) developed an FVII inhibitor. Case 1 was a 14-year-old boy with severe FVII deficiency (FVII activity <1%) with regular prophylaxis. The patient was a high-responder with high-titer FVII inhibitor (170 Bethesda Unit). This patient, who had a history of intracranial hemorrhage, had undergone brain surgery three times. The second patient was a 70-years old man with on-demand therapy that also developed a high-titer inhibitor (10 Bethesda Unit). This patient had experienced easy bruising and endured a few surgeries for his brain tumor and, finally, succumbed to the disease. Although the inhibitor formation is a rare phenomenon, it may result in a significant challenge to manage the affected patients.

Synthesis and characterization of (18)F-labeled active site inhibited factor VII (ASIS).

Activated factor VII blocked in the active site with Phe-Phe-Arg-chloromethyl ketone (active site inhibited factor VII (ASIS)) is a 50-kDa protein that binds with high affinity to its receptor, tissue factor (TF). TF is a transmembrane glycoprotein that plays an important role in, for example, thrombosis, metastasis, tumor growth, and tumor angiogenesis. The aim of this study was to develop an (18)F-labeled ASIS derivative to assess TF expression in tumors. Active site inhibited factor VII was labeled using N-succinimidyl-4-[(18)F]fluorobenzoate, and the [(18)F]ASIS was purified on a PD-10 desalting column. The radiochemical yield was 25 ± 6%, the radiochemical purity was >97%, and the pseudospecific radioactivity was 35 ± 9 GBq/µmol. The binding efficacy was evaluated in pull-down experiments, which monitored the binding of unlabeled ASIS and [(18)F]ASIS to TF and to a specific anti-factor VII antibody (F1A2-mAb). No significant difference in binding efficacy between [(18)F]ASIS and ASIS could be detected. Furthermore, [(18)F]ASIS was relatively stable in vitro and in vivo in mice. In conclusion, [(18)F]ASIS has for the first time been successfully synthesized as a possible positron emission tomography tracer to image TF expression levels. In vivo positron emission tomography studies to evaluate the full potential of [(18)F]ASIS are in progress.

Ionizable amphiphilic dendrimer-based nanomaterials with alkyl-chain-substituted amines for tunable siRNA delivery to the liver endothelium in vivo.

A library of dendrimers was synthesized and optimized for targeted small interfering RNA (siRNA) delivery to different cell subpopulations within the liver. Using a combinatorial approach, a library of these nanoparticle-forming materials was produced wherein the free amines on multigenerational poly(amido amine) and poly(propylenimine) dendrimers were substituted with alkyl chains of increasing length, and evaluated for their ability to deliver siRNA to liver cell subpopulations. Interestingly, two lead delivery materials could be formulated in a manner to alter their tissue tropism within the liver-with formulations from the same material capable of preferentially delivering siRNA to 1) endothelial cells, 2) endothelial cells and hepatocytes, or 3) endothelial cells, hepatocytes, and tumor cells in vivo. The ability to broaden or narrow the cellular destination of siRNA within the liver may provide a useful tool to address a range of liver diseases.

Coagulation factor VII variants resistant to inhibitory antibodies.

Replacement therapy is currently used to prevent and treat bleeding episodes in coagulation factor deficiencies. However, structural differences between the endogenous and therapeutic proteins might increase the risk for immune complications. This study was aimed at identifying factor (F)VII variants resistant to inhibitory antibodies developed after treatment with recombinant activated factor VII (rFVIIa) in a FVII-deficient patient homozygous for the p.A354V-p.P464Hfs mutation, which predicts trace levels of an elongated FVII variant in plasma. We performed fluorescent bead-based binding, ELISA-based competition as well as fluorogenic functional (activated FX and thrombin generation) assays in plasma and with recombinant proteins. We found that antibodies displayed higher affinity for the active than for the zymogen FVII (half-maximal binding at 0.54 ± 0.04 and 0.78 ± 0.07 BU/ml, respectively), and inhibited the coagulation initiation phase with a second-order kinetics. Isotypic analysis showed a polyclonal response with a large predominance of IgG1. We hypothesised that structural differences in the carboxyl-terminus between the inherited FVII and the therapeutic molecules contributed to the immune response. Intriguingly, a naturally-occurring, poorly secreted and 5-residue truncated FVII (FVII-462X) escaped inhibition. Among a series of truncated rFVII molecules, we identified a well-secreted and catalytically competent variant (rFVII-464X) with reduced binding to antibodies (half-maximal binding at 0.198 ± 0.003 BU/ml) as compared to the rFVII-wt (0.032 ± 0.002 BU/ml), which led to a 40-time reduced inhibition in activated FX generation assays. Taken together our results provide a paradigmatic example of mutation-related inhibitory antibodies, strongly support the FVII carboxyl-terminus as their main target and identify inhibitor-resistant FVII variants.

Prospective study of continuous infusion with Beriate® P in patients with severe haemophilia A undergoing surgery - a subgroup analysis.

INTRODUCTION: Inhibitor development in severe haemophilia A patients is currently the most serious complication of factor VIII (FVIII) treatment. Although continuous infusion (CI) of FVIII concentrate during surgical procedures in haemophilia A patients has been shown to be beneficial, some publications suggest that CI increases the risk of inhibitor generation. We conducted a prospective subgroup analysis to investigate if CI of the high-purity, pasteurized, plasma-derived FVIII concentrate Beriate(®) P during surgery increases the risk of inhibitor formation. MATERIALS AND METHODS: Patients with severe haemophilia A (FVIII:C <1%) were included if they presented with a negative history of previous inhibitors, had ≥ 50 exposure days, and had been scheduled for a planned surgical procedure. A bolus infusion (30-50 IU/kg body weight) of Beriate(®) P was administered intravenously and followed by CI at a rate of 3-4 IU/kg body weight/hour. Dose adjustments were subsequently made based on daily measurements of plasma FVIII activity. RESULTS: Five patients (aged 8-34 years) with severe haemophilia A were included. The surgical procedures ranged from teeth extraction to internal fixation of a fracture. There was no inhibitor generation with CI of Beriate(®) P in patients undergoing surgery, and we did not observe any complications due to re-bleeding or virus transmission. CONCLUSION: Beriate(®) P was efficacious, safe, and well tolerated during CI.

Role of hepsin in factor VII activation in zebrafish.

Factor VII, the initiator of the extrinsic coagulation cascade, circulates in human plasma mainly in its zymogen form, factor VII and in small amounts in its activated form, factor VIIa. However, the mechanism of initial generation of factor VIIa is not known despite intensive research using currently available model systems. Earlier findings suggested serine proteases factor VII activating protease and hepsin play a role in activating factor VII, however, it has remained controversial. In this paper we estimated the levels of factor VIIa and factor VII for the first time in zebrafish adult population and also reevaluated the role of the above two serine proteases in activating factor VII in vivo using zebrafish as a model system. Knockdown of factor VII activating protease and hepsin was performed followed by assaying for their effect on factor VIIa concentration and extrinsic coagulation as measured by the kinetic prothrombin time. Factor VII activating protease knockdown showed no change in kinetic prothrombin time and no effect on factor VIIa levels while hepsin knockdown increased the kinetic prothrombin time and significantly reduced the factor VIIa plasma levels. Our results thus indicate that hepsin plays a physiologically important role in factor VII activation and hemostasis in zebrafish.

Localized heuristic inverse quantitative structure activity relationship with bulk descriptors using numerical gradients.

State-of-the-art quantitative structure-activity relationship (QSAR) models are often based on nonlinear machine learning algorithms, which are difficult to interpret. From a pharmaceutical perspective, QSARs are used to enhance the chemical design process. Ultimately, they should not only provide a prediction but also contribute to a mechanistic understanding and guide modifications to the chemical structure, promoting compounds with desirable biological activity profiles. Global ranking of descriptor importance and inverse QSAR have been used for these purposes. This paper introduces localized heuristic inverse QSAR, which provides an assessment of the relative ability of the descriptors to influence the biological response in an area localized around the predicted compound. The method is based on numerical gradients with parameters optimized using data sets sampled from analytical functions. The heuristic character of the method reduces the computational requirements and makes it applicable not only to fragment based methods but also to QSARs based on bulk descriptors. The application of the method is illustrated on congeneric QSAR data sets, and it is shown that the predicted influential descriptors can be used to guide structural modifications that affect the biological response in the desired direction. The method is implemented into the AZOrange Open Source QSAR package. The current implementation of localized heuristic inverse QSAR is a step toward a generally applicable method for elucidating the structure activity relationship specifically for a congeneric region of chemical space when using QSARs based on bulk properties. Consequently, this method could contribute to accelerating the chemical design process in pharmaceutical projects, as well as provide information that could enhance the mechanistic understanding for individual scaffolds.

Inhibitors of the initiation of coagulation.

Initiation of blood coagulation occurs mainly through tissue factor (TF) that becomes exposed to blood following vascular injury. Cell-associated TF binds to the serine protease FVIIa and initiates a cascade of amplified zymogen activation reactions leading to thrombus formation. As TF-FVIIa directed inhibitors might achieve anticoagulant efficacy without significantly interfering with normal haemostasis, the TF-FVIIa complex is an interesting target in thrombosis-related disease. Various approaches have been used to inhibit the TF-FVIIa complex including active site-inhibited FVIIa, TF antibodies, tissue factor pathway inhibitor (TFPI), naturally occurring inhibitors, peptide exosite inhibitors and active site inhibitors. Several experimental studies using these inhibitors have displayed promise. However, none of these TF/FVIIa inhibitors has reached clinical testing. Further studies are required to evaluate the clinical efficacy of these novel inhibitors.

Intravascular inhibition of factor VIIa and the analogue NN1731 by antithrombin.

NN1731 is a recombinant activated factor VII (rFVIIa) analogue with increased intrinsic activity. This also applies to its reactivity towards antithrombin (AT), the role of which was investigated in a pharmacokinetic (PK) study. NN1731 or rFVIIa was administered to normal and haemophilia A dogs and elimination was measured by FVIIa clot activity, FVIIa- and FVIIa-AT antigen. In vitro AT complex formation was studied in canine plasma spiked with NN1731 or rFVIIa. Based on FVIIa antigen concentrations, PK profiles in normal and haemophilia A dogs were similar for NN1731 and rFVIIa with antigen half lives, t(½) ≈1·8 h. In contrast, PK profiles based on activity measurements were distinctly different. NN1731 induced a strong, short lasting (t(½) ≈0·5 h) pro-coagulant response, whereas rFVIIa induced a lower, longer lasting (t(½) ≈1·1 h) response. Western Blot and FVIIa-AT antigen analysis demonstrated in vivo AT complex formation that accounted for these divergences. AT complex formation with FVIIa or NN1731 in vitro in canine plasma was considerably slower than the in vivo reaction. The results suggest that in vivo inhibition by AT contributes significantly to define drug duration in haemophilia treatment with rFVIIa and in particular with the NN1731 analogue.

Lipid-like materials for low-dose, in vivo gene silencing.

Significant effort has been applied to discover and develop vehicles which can guide small interfering RNAs (siRNA) through the many barriers guarding the interior of target cells. While studies have demonstrated the potential of gene silencing in vivo, improvements in delivery efficacy are required to fulfill the broadest potential of RNA interference therapeutics. Through the combinatorial synthesis and screening of a different class of materials, a formulation has been identified that enables siRNA-directed liver gene silencing in mice at doses below 0.01 mg/kg. This formulation was also shown to specifically inhibit expression of five hepatic genes simultaneously, after a single injection. The potential of this formulation was further validated in nonhuman primates, where high levels of knockdown of the clinically relevant gene transthyretin was observed at doses as low as 0.03 mg/kg. To our knowledge, this formulation facilitates gene silencing at orders-of-magnitude lower doses than required by any previously described siRNA liver delivery system.

Identification of an anticoagulant peptide that inhibits both fXIa and fVIIa/tissue factor from the blood-feeding nematode Ancylostoma caninum.

Factor VIIa-tissue factor complex (fVIIa/TF) and factor XIa (fXIa) play important roles in the initiation and amplification of coagulation, respectively. They may be good targets for the development of novel anticoagulants to treat and prevent thromboembolic disease. In this study, we cloned, expressed and identified a novel anticoagulant peptide, AcaNAP10, from the blood-feeding nematode Ancylostoma caninum. AcaNAP10 showed potent anticoagulant activity and doubled the activated partial thromboplastin and prothrombin times at estimated concentrations of 92.9 nM and 28.8 nM, respectively. AcaNAP10 demonstrated distinct mechanisms of action compared with known anticoagulants. It inhibited fXIa and fVIIa/TF with IC(50) values of 25.76+/-1.06 nM and 123.9+/-1.71 nM, respectively. This is the first report on an anticoagulant that can inhibit both fXIa and fVIIa/TF. This anticoagulant peptide may be an alternative molecule for the development of novel anticoagulants.

Activity and regulation of factor VIIa analogs with increased potency at the endothelial cell surface.

BACKGROUND: Variants of recombinant factor VIIa (rFVIIa) with increased intrinsic activity have been developed to improve efficacy in the treatment of bleeding disorders in the future. The increased potency of FVIIa variants was demonstrated in limited in vitro and in vivo studies. However, further characterization of FVIIa variants is needed to evaluate their potential clinical use. METHODS: In the present study, we investigated the interactions of two FVIIa variants, FVIIa(Q) and FVIIa(DVQ), with plasma inhibitors, tissue factor pathway inhibitor (TFPI) and antithrombin (AT), and vascular endothelium. TF-FVIIa activity or its inhibition was measured directly in an amidolytic activity assay or for its ability to activate factor X. RESULTS: Both TFPI and AT/heparin inhibited the FVIIa variants more rapidly than the wild-type (WT) FVIIa in the absence of tissue factor (TF). In the presence of TF, TFPI, TFPI-Xa, and AT/heparin inhibited FVIIa and FVIIa variants at similar rates. Although the WT FVIIa failed to generate significant amounts of FXa on unperturbed endothelial cells, FVIIa variants, particularly FVIIa(DVQ), generated a substantial amount of FXa on unperturbed endothelium. Annexin V fully attenuated the FVIIa-mediated activation of FX on unperturbed endothelial cells. On stimulated human umbilical vein endothelial cells, FVIIa and FVIIa variants activated FX at similar rates, and annexin V blocked the activation only partly. AT/heparin and TFPI-Xa inhibited the activity of FVIIa and FVIIa variants bound to endothelial cell TF in a similar fashion. Interestingly, despite significant differences observed in FXa generation on unperturbed endothelium exposed to FVIIa and FVIIa analogs, no differences were found in thrombin generation when cells were exposed to FVIIa or FVIIa analogs under plasma mimicking conditions. CONCLUSION: Overall, the present data suggest that although FVIIa variants generate substantial amounts of FXa, they do not generate excessive thrombin on the surface of endothelium.

Quality of life is associated to the orthopaedic status in haemophilic patients with inhibitors.

Inhibitors represent one major complication of haemophilia treatment, as they increase the risk of bleeding, physical disability and mortality. The Cost Of Care Inhibitors Study (COCIS) showed that modern strategies applied to manage patients with inhibitors adsorb high amounts of resources but provide satisfactory levels of Health-Related Quality-of-Life (HR-QoL). This paper focuses on determinants of HR-QoL in inhibitory patients. Fifty adult patients, enrolled by 11 Italian Haemophilia Centres, were clinically assessed and filled in two HR-QoL generic questionnaires: the EuroQol instrument (EQ-5D) and the Short Form-36 (SF-36). According to our results, bleeding frequency and inhibitor titres were not found associated with HR-QoL. Global HR-QoL, and in particular the physical component of wellbeing in these patients was found negatively associated with their orthopaedic condition: the EQ-5D Visual Analogue Scale (P<0.001) scores, the SF-36 domain 'physical functioning' and 'physical component summary' (P<0.01) scores were found significantly correlated with the orthopaedic joint score, even after adjusting for patients' age. These results were confirmed by those from the EQ-5D profile. To conclude, the COCIS study is the first study showing that HR-QoL in inhibitory patients is impaired by their orthopedic status, while other aspects do not seem to influence patients' global wellbeing. Our results suggest that while the management of this complication is satisfactory, the attention has now to be focused on the prevention of the orthopaedic problems in these patients, which nowadays constitute one of the most important aspects to be considered in the haemophilia care.

Generation of potent coagulation protease inhibitors utilizing zinc-mediated chelation.

Inhibition of coagulation proteases such as thrombin, fXa, and fVIIa has been a focus of ongoing research to produce safe and effective antithrombotic agents. Herein, we describe a unique zinc-mediated chelation strategy to streamline the discovery of potent inhibitors of fIIa, fXa, and fVIIa. SAR studies that led to the development of selective inhibitors of fXa will also be detailed.