Novel biotherapeutics can cause infusion-related reactions in patients, which may only become apparent in first-in-man trials. The FDA recommends in its recent definitiveGuidance for Industry for Immunogenicity Assessment for Therapeutic Protein Products: “in vitro assessments of the capacity of such therapeutic protein products to mediate cellular activation, including proliferation and cytokine release in human whole blood or peripheral blood mononuclear cells are recommended” prior to first-in-man use.
To provide more information to drug developers before drugs reach clinical trials, ProImmune has developed ProStorm®, an in vitro cytokine release assay which can help to predict the likelihood of first infusion reactions. Since its launch in 2013 our ProStorm® has been deployed on a very broad range of biotherapeutic strategies, from proteins, to mAbs, ADCs, bis-pecifics and more complex novel biological entities with data from the assay being submitted routinely to regulatory agencies. With a typical core turnaround time of only 4 weeks ProStorm® is also a rapid service helping you make timely decisions in your development program.
We source blood samples from a donor cohort chosen to match the needs of your project. Most often, we will use cohorts of at least 20 healthy volunteers, but we are able to source donors with known conditions if this is required.
The assay can be set up with fresh whole blood, isolated PBMC with drug that is either in solution or immobilized, depending on the customer requirements.
We use your drug preparation at a range of concentrations designed to mimic the peak exposure during a first infusion.
We add your drug preparation to the blood or PBMC samples, and after incubation, harvest the serum to measure cytokine levels. Typically, we would measure TNFα, IFNɣ, IL-2, IL-4, IL-6, IL-8 and IL-10, but in consultation with you we will select the best panel. Cytokine levels are measured using our ProArray Ultra® technology for the most accurate quantification. Our team analyses your data to give you results that can be used in informing the next stages of your research.
We present two types of analysis as standard – plots showing the response from your donor cohort by cytokine for each drug/concentration, and a threshold (cut-point) analysis to indicate potential risk.
Figure 1: – Prostorm® results. Cytokine Response Data for IL-6. Responses from a cohort of 29 donors, stimulated with (left to right) Remicade®, aggregated Remicade®, Erbitux®, Campath®, Herceptin® and Vectibix®, at a range of concentrations. Medians are indicated by red lines. Particularly notable are the high responses from Campath®, and from aggregated Remicade®.
In addition to plots showing the cytokine responses of your whole donor cohort to each drug and dose combination tested, we also present a threshold (cut-point) analysis. In this analysis the test article therapeutic is typically compared to Erbitux®(Cetuximab), as this is known to elicit a low incidence of first infusion-related reactions.
Figure 2: example threshold analysis
This analysis approach is particularly powerful when used across a range of drug concentrations and when used with a large donor cohort. The results shown are from 29 healthy donors, and show the IL-6 response to 100µg/ml drug.
Figure 3: Erbitux® responses and 95th centile thresholds applied across increasing drug concentrations, IL-6 responses from a 29-donor cohort.
We will also typically include Campath® (Alemtuzamab) as administration of this mAb is associated with a high incidence of first-infusion reactions, and can serve as a useful high response comparator.
Figure 4: Campath® responses with Erbitux® 95th centile thresholds applied across increasing drug concentrations, IL-6 responses from a 29-donor cohort.
A particularly attractive feature of the assay is its suitability for assessing fully formulated therapeutics. This allows the effects of changes in formulation to be easily assessed. In one of our exploratory studies at ProImmune, we investigated the cytokine responses to Infliximab (Remicade®) and aggregated Remicade®. The results (figure 5) clearly show the increased reactivity of fresh blood to the aggregated formulation.
Figure 5: Remicade® and Aggregated Remicade® responses with Erbitux® 95th centile thresholds applied across increasing drug concentrations, IL-6 responses from a 29-donor cohort. Positive responders are indicated by filled data points.
Figure 6: For a range of well known therapeutic drugs in the market place, where the clinically observed incidence of cytokine release reactions is known a good correlation is seen between the ProStorm® assay results and clinical incidence of cytokine release.
Q: Does unexpected high cytokine release in a ProStorm® project cause problems with the regulatory submission?
A: Understanding the hazard of potential cytokine release is important for any prospective clinical study. If a hazard is identified from the assay, usually numerous options are available for mitigating the hazard going into the clinic. These often include: adjusting the dose range, extending drug release time, changing mode of administration, planning for treatment of clinical effects of cytokine release, another chance to look at manufacturing / fill finish related issues (where relevant).
Q: Which cytokine release assay works best: whole blood or PBMC, soluble or plate bound?
A: The most appropriate assay format will depend on the test articles under investigation and in some situations more than one testing format is advisable. Some early publications suggested that blood based assays did not produce the sensitivity of PBMC assays. Generally we find that this is not the case and our optimized whole blood assay shows very good sensitivity with commercially available drugs known to cause cytokine release. The lack of manipulation of whole fresh blood as a test system also makes this version an attractive assay variant.