Ustekinumab and Anti-Ustekinumab Antibody, DoseASSURE™ UST

Serum (preferred) or plasma

3 mL

1 mL (Note: This volume does not allow for repeat testing.)

Red-top tube, gel-barrier tube, plasma EDTA tube, or plasma heparin tube

Provides ustekinumab drug concentration and anti‐ustekinumab antibodies in order to optimize treatment and facilitate clinical decision‐making.

This assay may be helpful in any patients on ustekinumab therapy for Crohn's disease, psoriasis, or other autoimmune conditions.

Drug concentration should be interpreted with confirmation of specimen collection timing.

Non‐trough concentrations may be misleading.

Trough blood collection (just before or within 24 hrs. of next dose) is suitable because target ranges and therapeutic cut‐offs have been established in clinical studies using trough concentration.

The drug half‐life should be taken into consideration when interpreting results from non‐perfect trough collections.

Some primary non‐responders have inadequate clinical response despite adequate trough levels.

As with other biologics, the optimal ustekinumab concentration depends upon patient‐specific factors including co‐morbidities, disease and desired therapeutic endpoint.

Positive anti‐ustekinumab antibodies should be interpreted in the context of the concomitant free ustekinumab drug level.

High serum biotin concentrations in patients taking biotin supplements may cause an interference in this assay. Patients may be advised to stop biotin consumption at least 72 hours prior to sample collection.

Electrochemiluminescence immunoassay (ECLIA)

Ustekinumab drug level: <0.1 μg/mL

• Result ≥0.1 μg/mL indicates detection of ustekinumab

• In the presence of anti-ustekinumab antibodies, the ustekinumab drug level reflects the free, antibody-unbound fraction of ustekinumab in serum.

Anti-ustekinumab antibody: <40 ng/mL

• Result ≥40ng/mL indicates detection of anti-ustekinumab antibodies.

Drug Assay: The ustekinumab drug level typically reflects the antibody-unbound (the free fraction) of ustekinumab when serum anti-ustekinumab antibodies are present. In the absence of anti-ustekinumab antibodies, the ustekinumab drug level typically reflects the total ustekinumab concentration in serum.

Anti-drug Antibody Assay: This anti-ustekinumab antibody assay is “drug-tolerant,” that is, the presence of serum ustekinumab does not impede the detection and quantitation of anti-ustekinumab antibodies. This anti-ustekinumab antibody assay is specific; antibodies against other biologic drugs do not cross-react with this assay. All positive anti-ustekinumab antibody results are verified by a confirmatory test.

Both drug and anti-drug antibody assays have been developed and validated using the FDA guidance document Assay Development and Validation for Immunogenicity Testing of Therapeutic Protein Products (2016) as a reference.