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Phenylketonuria (PKU), a deficiency in the activity of the enzyme phenylalanine hydroxylase, leads to toxic levels of phenylalanine (Phe) in the blood and brain. Pegvaliase (recombinant Anabaena variabilis phenylalanine ammonia lyase conjugated with polyethylene glycol) is approved to manage PKU in patients aged greater than or equal to 18 years in the United States and in patients aged greater than or equal to 16 years in the European Union. Pharmacokinetic, pharmacodynamic, and immunogenicity results from five open‐label pegvaliase trials were assessed. Studies with induction/titration/maintenance (I/T/M) dosing regimens demonstrated pharmacokinetic stabilization and sustained efficacy associated with maintenance doses (20, 40, or 60 mg/day). Immune‐mediated pegvaliase clearance was high during induction/titration phases when the early immune response was peaking. The combination of low drug dosage and high drug clearance led to low drug exposure and minimal decreases in blood Phe levels during induction/titration. Higher drug exposure and substantial reductions in blood Phe levels were observed later in treatment as drug clearance was reduced due to the maturation of the immune response, which allowed for increased dosing to target levels. The incidence of hypersensitivity reactions was temporally associated with the peaking of the early antidrug immune response and decreased with time as immune response matured after the first 6 months of treatment. These results support an I/T/M dosing regimen and suggest a strategy for administration of other nonhuman biologics to achieve efficacy and improve tolerability.

Transthyretin amyloidosis with cardiomyopathy (ATTR-CM) is a progressive, often fatal disease. Nexiguran ziclumeran (nex-z) is an investigational therapy based on CRISPR-Cas9 (clustered regularly interspaced short palindromic repeats and associated Cas9 endonuclease) targeting the gene encoding transthyretin ( ). In this phase 1, open-label trial, we administered a single intravenous infusion of nex-z to patients with ATTR-CM. Primary objectives included assessment of the effect of nex-z on safety and pharmacodynamics, including the serum TTR level. Secondary end points included changes in N-terminal pro-B-type natriuretic peptide (NT-proBNP) levels, high-sensitivity cardiac troponin T levels, the 6-minute walk distance, and the New York Heart Association (NYHA) class. A total of 36 patients received nex-z and completed at least 12 months of follow-up. Of these patients, 50% were in NYHA class III and 31% had variant ATTR-CM. The mean percent change from baseline in the serum TTR level was -89% (95% confidence interval [CI], -92 to -87) at 28 days and -90% (95% CI, -93 to -87) at 12 months. Adverse events were reported in 34 patients. Five had transient infusion-related reactions, and two had transient liver-enzyme elevations that were assessed as treatment-related. Serious adverse events, most of which were consistent with ATTR-CM, were reported in 14 patients. The geometric mean factor change from baseline to month 12 was 1.02 (95% CI, 0.88 to 1.17) in the NT-proBNP level and 0.95 (95% CI, 0.89 to 1.01) in the high-sensitivity cardiac troponin T level. The median change from baseline to month 12 in the 6-minute walk distance was 5 m (interquartile range, -33 to 49). A total of 92% of the patients had either improvement or no change in their NYHA class. In this phase 1 study involving patients with ATTR-CM, treatment with a single dose of nex-z was associated with transient infusion-related reactions and consistent, rapid, and durable reductions in serum TTR levels. (Funded by Intellia Therapeutics and Regeneron Pharmaceuticals; ClinicalTrials.gov number, NCT04601051.).

Interleukin-6 (IL6)-mediated signaling is known to play a role in pathogenesis and resistance in several cancers like multiple myeloma (MM). In this report we used the IL6-dependent 7TD1 murine B-cell hybridoma as an in vitro model to study the interactions between IL6-signaling pathways and the development of dexamethasone resistance. Though in initial stages, 7TD1 cells grew IL6-dependent and were sensitive to dexamethasone-induced apoptosis, chronic exposure to dexamethasone led to a dexamethasone-resistant phenotype (7TD1-Dxm) that grew independent of exogenous IL6. While IL6-mediated JAK/STAT3 and PI3K/AKT signaling was important for proliferation of both cell lines, as shown in proliferation assays using the respective pathway inhibitors, AG490 and LY294002, the resistant cells were insensitive to induction of apoptosis using the same. STAT3 was constitutively phosphorylated in resistant cells and inhibition of its dimerization induced apoptosis but did not alter their insensitivity to dexamethasone. Our results suggest a role of entities downstream of IL6-mediated JAK/STAT3 signaling in development of dexamethasone resistance by 7TD1-Dxm cells.

Multiple myeloma (MM) is a cancer that resembles terminally differentiated plasma cells. Unfortunately, patients diagnosed with MM have a poor prognosis: only 31% of patients live five years after diagnosis. Epidemiological studies suggest that the cytokine interleukin 6 (IL6) may play a role in stimulating initiation and/or progression of this disease. Therefore evaluating the role of IL6 in cell proliferation and death could provide insight into the development and progression of MM. In previous studies, 7TD1 cells, a murine B cell hybridoma, have been used as a model for evaluating IL6 actions. In this model, IL6 has been shown to inhibit apoptosis induced by dibutyryl cAMP (dbcAMP) as well as some chemotherapies. These preliminary studies suggest IL6 may stimulate progression of MM in two ways: directly stimulating growth and inhibiting chemotherapy induced apoptosis. Here we evaluated how IL6 may be determining cell fate using three approaches. First, we evaluated how IL6 stimulates proliferation. We found that IL6 treatment of 7TD1 cells leads to an increase in cyclin D1 expression. This change in expression appears to be dependent on activation of the IL6 regulated STAT3 signaling pathway and is suppressed by the addition of dbcAMP. Second, we evaluated the mechanism by which IL6 may inhibit dbcAMP induced apoptosis. Results from these studies suggest that dbcAMP indirectly activates apoptosis and IL6 inhibits apoptosis by inducing changes in expression of the apoptosis regulator XIAP. Results from the two previous approaches suggested IL6 promotes changes in gene expression to stimulate proliferation and inhibit apoptosis. Therefore, in the third approach we identified IL6 regulated genes. The IL6 regulated gene set was then compared to gene databases available for MM. Many of the genes identified in both gene sets function in regulating proliferation and can provide clues to the role of IL6 in stimulating development and/or progression of MM. In addition, evaluating IL6 regulated genes is the first step in identifying the unique set of genes produced after combined IL6 and dbcAMP treatment. Identification of this gene set will provide information on inhibition of apoptosis and potentially provide new insight into mechanisms of chemotherapy resistance.