The disclosure provides, e.g., compositions, systems, and methods for targeting, editing, modifying, or manipulating a host cell's genome at one or more locations in a DNA sequence in a cell, tissue, or subject. Gene modifying systems for treating phenylketonuria (PKU) are described.

The present invention provides an improved process for lipid nanoparticle formulation and mRNA encapsulation. In some embodiments, the present invention provides a process of encapsulating messenger RNA (mRNA) in lipid nanoparticles comprising a step of mixing a solution of pre-formed lipid nanoparticles and mRNA.

Provided herein are methods of treating phenylketonuria by normalizing levels of amino acids, neurotransmitters, and neurotransmitter metabolites in a subject having phenylketonuria.

Compositions and regimens useful in treating phenylketonuria are provided. The compositions include recombinant adeno-associated virus (rAAV) with a transthyretin enhancer and promoter driving expression of a human phenylalanine hydroxylase.

Disclosed herein are cells and cell lines that are selected for retention of at least two exogenous nucleic acid constructs using a single selective pressure. Also disclosed herein are compositions and methods for generating recombinant cells and cell lines using a single selective pressure.

Provided herein are methods of treating a subject having a disease or disorder associated with a PAH gene mutation. The methods generally comprise administering to the subject a therapeutically effective does of a recombinant adeno-associated virus (rAAV) that can express a phenylalanine hydroxylase (PAH) polypeptide in a cell and thereby restore PAH gene function in the subject.

A method of restoring activity in phenylalanine hydroxylase is provided. The method comprises exposing the phenylalanine hydroxylase to shikimic acid, a functionally equivalent analog thereof, a pharmaceutically acceptable salt of shikimic acid or analog thereof, or combinations thereof. A method of screening for allosteric activators for a target enzyme is also provided comprising the steps of: denaturing the target enzyme with a first chaotropic agent to yield denatured enzyme, incubating the denatured enzyme with a candidate compound under denaturing conditions to allow enzyme refolding, and assaying enzyme activity in the presence of enzyme substrate and a candidate compound; and if enzyme activity of the denatured enzyme was restored in step i) by at least about 10% of residual enzyme activity, denaturing the target enzyme with a second chaotropic agent to yield denatured enzyme, incubating the denatured enzyme with the candidate compound under non-denaturing conditions to allow enzyme refolding, and assaying enzyme activity in the presence of enzyme substrate and the candidate compound, wherein an increase in enzyme activity of at least about 10% of residual enzyme activity indicates that the candidate compound is an allosteric activator of the target enzyme.

The present invention provides, among other things, multimeric coding nucleic acids that exhibit superior stability for in vivo and in vitro use. In some embodiments, a multimeric coding nucleic acid (MCNA) comprises two or more encoding polynucleotides linked via 3 ends such that the multimeric coding nucleic acid compound comprises two or more 5 ends.

A lentiviral vector system for expressing a lentiviral particle is disclosed. The lentiviral vector system includes a therapeutic vector. The therapeutic vector comprises a phenylalanine hydroxylase (PAH) sequence for expressing at least one of PAH or a variant thereof, wherein the PAH sequence is truncated.

Provided herein are adeno-associated virus (AAV) compositions that can restore phenylalanine hydroxylase (PAH) gene function in cell. Also provided are methods of use of the AAV compositions, and packaging systems for making the AAV compositions.