Spermines are naturally abundant
polyamines that partially condense
nucleic acids and exhibit the proton-sponge effect in an acidic environment.
However, spermines show a limited efficiency for transfecting nucleic
acids because of their low molecular weight. Therefore, spermines
need to be modified to be used as nonviral vectors for nucleic acids.
Here, we synthesized linear bisspermine as well as a linear and dendritic
tetraspermine with different molecular architectures. These oligospermines
were self-assembled into polyplexes with siRNA. The structure–activity
relationship of the oligospermines was evaluated in terms of their
efficiency for delivering siRNA into a nonsmall cell lung carcinoma
cell line. Oligospermines displayed minimal cytotoxicity but efficient
siRNA condensation and showed better stability against polyanions
than polyethylenimine. The morphology of the polyplexes was strongly
affected by the oligospermine architecture. Linear tetraspermine/siRNA
polyplexes showed the best gene-silencing efficiency among the oligospermines
tested at both the mRNA and protein expression levels, indicating
the most favorable structure for siRNA delivery.
The implementation of clinically relevant drug product specifications (CRDPS) depends on establishing a link between in vitro performance and in vivo exposure. The scientific community, including regulatory agencies, relies on biopharmaceutics tools on the in vitro performance side, while to enable the link to in vivo exposure, physiologically based pharmacokinetic (PBPK) modeling offers much promise. However, when it comes to PBPK applications in support of CRDPS, otherwise called physiologically based biopharmaceutics models (PBBM), the tools are not yet at the desired level. Currently, it is not possible to integrate detailed variations in chemistry, manufacturing and controls (CMC) attributes and parameters into these models in a way that can consistently predict their effect on local and systemic drug exposure. Specifically, to achieve the desired level, there is a need to advance the science and policy of PBBM. This manuscript summarizes the proceedings of a three-day workshop where the following themes were discussed: 1) Challenges in the development and implementation of in vitro biopredictive tools needed for successful mechanistic modeling; 2) Best practices in model development, verification and validation; and 3) Appropriate terminology (e.g., PBBM vs. PBPK models for biopharmaceutics applications) and applications of PBBM in support of drug product quality.
The apical sodium dependent bile acid transporter (ASBT) and sodium-taurocholate cotransporting polypeptide (NTCP) are potential prodrug targets, but the structural requirements for these transporters are incompletely defined. The objective of this study was to evaluate the effect of C-3 and C-7 substitution on bile acid interaction with these bile acid transporters. Nineteen bile acid analogues were tested against ASBT and NTCP for binding, as well as translocation. Results indicated that ASBT and NTCP accommodated a wide range of substituents for binding, but all major C-7 modifications resulted in analogues that did not demonstrate active uptake by either ASBT or NTCP. A C-3 modification that was not tolerated at C-7 still afforded translocation via ASBT and NTCP, confirming the relative unacceptability of C-7 modification. Both ASBT and NTCP demonstrated a generally similar binding potency. Results suggest that drug conjugation to the C-3 hydroxyl group, rather than C-7, has potential to lead to a successful prodrug targeting ASBT and NTCP.
Purpose-Type of inhibition (e.g. competitive, noncompetitive) is frequently evaluated to understand transporter structure/function relationships but reliability of nonlinear regression to correctly identify inhibition type has not been assessed. The purpose was to assess the ability of nonlinear regression to correctly identify inhibition type.Methods-This aim was pursued through three objectives that compared the competitive, noncompetitive, and uncompetitive inhibition models to best fit simulated competitive and noncompetitive data. The first objective involved conventional inhibition data and entailed simulated data for the common situation where substrate concentration was fixed at a single level but inhibitor concentration varied. The second objective involved Dixon-type data where both substrate and inhibitor concentrations varied. A third objective involved nonconventional inhibition data, where substrate concentration was varied and inhibitor was fixed at a single concentration.
SSTS significantly enhanced therapeutic benefits associated with the use of T-oligo and can be developed as a delivery vehicle for its in-vivo therapeutic applications.
A variety
of delivery vehicles use spermine as a polycationic component
to form complexes with nucleic acids. Thus, we investigated the influence
of molecular architecture, amine density, and molecular weight of
oligospermines on its binding to nucleic acids. We report the synthesis
of mono, bis, and tetraspermines with linear, cyclic, dendritic, and
quatrefoil architecture. The effect of molecular weight was more pronounced
in linear oligospermines than their cyclic counterparts. Oligospermines
with similar amine density but different molecular architectures exhibited
different binding profiles. Among all oligospermines evaluated, dendritic
tetraspermine exhibited the highest binding affinity. Atomistic molecular
dynamics simulations also indicated higher affinity for dendritic
tetraspermine to siRNA than its linear counterpart suggesting the
importance of spermine geometry in binding to nucleic acids. Importantly,
dendritic tetraspermine was less toxic than linear tetraspermine,
suggesting its potential in nucleic acid delivery.
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