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Test Code RAVMP Ravulizumab Monitoring Panel, Serum


Ordering Guidance


To measure only serum concentration of ravulizumab, order RAVU / Ravulizumab, Serum.



Specimen Required


Patient Preparation:

1. Fasting preferred.

2. Suggest discontinuing natalizumab at least 4 weeks prior to testing for ravulizumab quantitation in serum. Patient should consult the healthcare provider who prescribed this drug to determine if discontinuation is an option. If not, ok to proceed with testing while taking natalizumab.

Supplies: Aliquot Tube, 5 mL (T914)

Collection Container/Tube: Red top (serum gel/SST are not acceptable)

Submission Container/Tube: 2 Plastic vials

Specimen Volume: 2 mL in 2 plastic vials, each vial containing 1 mL

Collection Instructions:

1. Draw blood immediately before next scheduled dose.

2. Immediately after specimen collection, place the tube on wet ice.

3. After sample has clotted on wet ice, centrifuge at 4° C and aliquot serum into two 5 mL plastic vials.

4. Freeze specimen within 30 minutes of centrifugation. Sample must be placed on dry ice if not frozen immediately.


Secondary ID

618645

Useful For

Monitoring of complement blockage by ravulizumab

 

Assessing the response to ravulizumab therapy

 

Assessing the need for dose escalation

 

Evaluating the potential for dose deescalation or discontinuation of therapy in remission states

 

Monitoring patients who need to be above a certain ravulizumab concentration in order to improve the odds of a clinical response for therapy optimization

Highlights

Ravulizumab is a therapeutic monoclonal antibody targeting complement C5 with a longer half-life than eculizumab. Monitoring the complete complement blockade by eculizumab has allowed personalized therapy in specific settings. Similar action is expected with ravulizumab. Ravulizumab has 4 different amino acids from eculizumab, which allow greater affinity for the FcRn immunoglobulin receptor and change the affinity of the molecule for C5.

 

Therapeutic drug monitoring of ravulizumab may be useful when patients need to be above a certain target or therapeutic threshold of the monoclonal antibody concentration to improve odds of a clinical response for therapy optimization or potential dose deescalation or discontinuation of therapy in remission states.

Profile Information

Test ID Reporting Name Available Separately Always Performed
RAVU Ravulizumab, S Yes Yes
RAVUM Ravulizumab Complement Blockage, S No Yes
RAVIN Ravulizumab Interpretation, S No Yes

Method Name

RAVUM: Enzyme-Linked Immunosorbent Assay (ELISA)

RAVU: Liquid Chromatography Tandem Mass Spectrometry, High Resolution Accurate Mass (LC-MS/MS HRAM)

Reporting Name

Ravulizumab Monitoring Panel, S

Specimen Type

Serum
Serum Red

Specimen Minimum Volume

1 mL in 2 plastic vials, each vial containing 0.5 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Frozen 14 days
Serum Red Frozen 14 days

Reject Due To

Gross hemolysis Reject
Gross lipemia Reject
Gross icterus OK

Clinical Information

Ravulizumab (Ultomiris, Alexion Pharmaceuticals) is a humanized hybrid monoclonal antibody (IgG2/IgG4) that blocks complement C5 cleavage, thereby preventing the activation of the proinflammatory effects of C5a and the cytolytic effects of the membrane attack complex (MAC) formed by C5b-C9.

 

The dosing regimen for ravulizumab is weight-based, and after a loading dose schedule, the maintenance therapy requires administration intravenously every 8 weeks. Therapy efficacy may be monitored by measuring efficiency of complement blockade. Ravulizumab will affect complement function assays that rely on the formation of the MAC to generate cell lysis. Validation studies performed by Mayo Clinic show that the alternative pathway (AH50) enzyme-linked immunosorbent assay is the most helpful of the complement tests to monitor efficacy of the complement blockage by ravulizumab. Ravulizumab serum concentrations greater than 200 mcg/mL inhibited the AH50 activity completely, and undetectable activity was measured at all subsequent tested concentrations up to 1000 mcg/mL.(1)

 

Some patients whose serum concentrations persist above therapeutic targets with complete complement blockade could benefit from dose deescalation or prolonged infusion intervals. Therapeutic drug monitoring of ravulizumab could result in cost-savings and improved quality of life if target therapeutic concentrations can be achieved with complete complement system blockage at less frequent dosing intervals.

Reference Values

RAVULIZUMAB COMPLEMENT BLOCKAGE:

≥46% normal

 

RAVULIZUMAB:

Lower limit of quantitation =5.0 mcg/mL

>175 mcg/mL: Therapeutic concentration for paroxysmal nocturnal hemoglobinuria and atypical hemolytic uremic syndrome

Interpretation

Target trough therapeutic concentrations (immediately before next infusion) of ravulizumab are expected to be above 175 mcg/mL for paroxysmal nocturnal hemoglobinuria and atypical hemolytic uremic syndrome. Pharmacodynamic studies of complement blockage may also be recommended for patients undergoing therapy.

 

For the complement blockage monitoring of ravulizumab:

-When ravulizumab is present in serum at concentrations around 50 mcg/mL, the results range from 20% to 29% of normal.

-When ravulizumab concentrations are around 100 mcg/mL, the results range from below 10% to 13% of normal.

-When ravulizumab concentrations are greater than 200 mcg/mL, the results are below the limit of quantitation of the assay (<10% of normal).

Method Description

The Wieslab enzyme-linked immunosorbent assay (ELISA) complement assay for the alternative pathway combines principles of the hemolytic assay for complement activation with the use of labeled antibodies specific for neoantigens produced as a result of complement activation. The microtiter plate strips are coated with lipopolysaccharide. Patient serum is diluted in diluent containing specific blocker to ensure that only the alternative pathway is activated. During the first incubation, the diluted patient serum in the wells is activated by the coating. The wells are then washed and C5b-9 (membrane attack complex: MAC) is detected with a specific alkaline phosphatase labeled antibody to the neoantigen expressed during MAC formation. After a final wash, an alkaline phosphatase substrate is added. The amount of alternative pathway complement activity correlates with the color intensity of the solution and is measured in terms of absorbance (optical density).(Nordin JG, Truedsson L, Sjoholm A. New procedure for detection of complement deficiency by ELISA. Analysis of activation pathways and circumvention of rheumatoid factor influence. J Immunol Methods. 1993;166(2):263-270; Frazer-Abel A, Sepiashvili L, Mbughuni MM, Willrich MA. Overview of laboratory testing and clinical presentations of complement deficiencies and dysregulation. Adv Clin Chem. 2016;77:1-75. doi:10.1016/bs.acc.2016.06.001)

 

Ravulizumab concentration is extracted from serum and measured by liquid chromatography high-resolution accurate-mass mass spectrometry.(Unpublished Mayo method)

Day(s) Performed

Varies

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information

80299

86161

LOINC Code Information

Test ID Test Order Name Order LOINC Value
RAVMP Ravulizumab Monitoring Panel, S 101923-1

 

Result ID Test Result Name Result LOINC Value
609500 Ravulizumab Complement Blockage, S 74520-8
609420 Ravulizumab, S 97184-6
619952 Ravulizumab Interpretation 59462-2