TRACKER is a simple test for the quantitative determination of biological drug concentration and anti-drug antibodies in human blood samples. These two parameters help the clinican to make rational decisions for patient treatment management.

Results from TRACKER will indicate biotherapies levels in the patient’s blood, and if the patient has developed antibodies to this biotherapy which may may prevent the drug from working effectively.

Drug trough levels and anti-drug antibodies appear to be two parameters that enable the clinician, based on patient’s clinical status, to make rational therapeutic decisions in different clinical situations:

– Guide therapy after a treatment failure and follow-up therapeutic adjustment (switch or optimization)

– Predict clinical response 

– Guide treatment downscaling for patients in remission 

– Reduce treatment costs by implementing a rational decision-making patient care management 

– Decrease the risk of allergic reactions during infusion or other adverse effects

– Predict postoperative complications 

The bioavailability of a drug is the degree to which a drug is available to a  target a specific molecule after administration or at a given time. e.g. the trough Adalimumab concentration is a good indicator of the bioavailability of Adalimumab.

For all of the biotherapies we monitor, published data indicate that trough drug concentration and clinical response to the treatment are closely linked:
– Lower trough level than the therapeutic threshold is associated with a loss or a partial response to the treatment and a reappearance of the clinical symptoms
– Trough level concentrations higher than the therapeutic window do not bring additional clinical benefits and increase risks of iatrogenic effects and costs of treatment

Various factors affect the pharmacokinetic of a biotherapy, including heterogeneity of patients, their pathology, the use of other medications, and more importantly anti-drug antibodies appearance.
– The presence of anti-drug antibodies has a direct impact on the treatment efficacy by blocking the action of the drug
– Furthermore, anti-drug antibodies increase the clearance and reduce the drug concentration, leading to loss of clinical efficacy

All biotherapies are immunogenic and trigger the production of anti-drug antibodies. Studies show variability in anti-drug antibodies incidence. The frequency of anti-drug antibodies incidence varies according to the molecule and depends on:
– the dose administered,
– the treatment scheme,
– the immunogenicity of each molecule, linked to their structure,
– the individual pharmacokinetic variability.

The information has to be used along with clinical information and other analysis results. According to a simplified therapeutic decision algorithm the physician could make his decision for instance in the case of patient expencing a loss of response:

In 2019 an expert consensus development meeting consisting of members of the BRIDGe group revised and published new consensus for the monitoring of responding patients at the end of induction and during maintenance treatment of biologics. The expert committee also recommended the use of TDM in patients with primary or secondary loss of response to guide treatment management. More information here

The sample should be drawn by venipuncture just before the next infusion in order to be at Trough Level of the drug. 

The samples should be collected prior to next drug administration (i.e. trough level).
The minimum volume require to performed the analysis is 300 µl (for both drug and anti-drug antibodies analyses).
The samples should be drawn in plain red top tubes or serum separator tubes (SST).
The samples should be stored refrigerated between +2°C and +4°C. If the sample analysis is delayed by more than 5 days, the samples should be frozen at -20°C.

Lipemic sera should be avoided, as well as samples which have been frozen and defrosted more than once.
To avoid any non-specific binding, samples which have been frozen for more than 6 months or which are cloudy, should be centrifuged and filtered.

TRACKER provides quantitative results for both drug and anti-drug antibodies. For example, the results are expressed in µg/ml for the drug measurement and in ng/ml for anti-drug antibodies determination.

The test request has to be accompanied by the Test Requisition Form containing all the required information and especially the actual drug administration regimen (dosage, frequency, date of last injection, other treatments, etc.)