The International Working Group on TTP (IWG TTP) has developed an updated proposal for monitoring patients with congenital thrombotic thrombocytopenic purpura (cTTP) who receive ADAMTS13 replacement therapy with Adzynma.
The proposal was revised following discussion by the IWG TTP Advisory Board during the 2026 ISTH Congress in Paris.
The work follows reports of anti-ADAMTS13 antibodies in patients receiving recombinant ADAMTS13, including a case described in a U.S. Food and Drug Administration communication and a subsequently published case from the Japanese TTP group. These reports highlight the importance of continued vigilance, consistent monitoring, and international collaboration as the use of recombinant ADAMTS13 expands.
Proposed Monitoring Approach
IWG TTP recommends consideration of the following approach for patients receiving ADAMTS13 replacement therapy:
1. Monitor treatment efficacy and ADAMTS13 activity
Treatment efficacy should be reviewed at least every three months with trough ADAMTS13 activity levels. Peak ADAMTS13 levels within 48 hours following an infusion should be considered every six months, in addition to routine monitoring of platelet counts and markers of hemolysis.
2. Monitor for binding anti-ADAMTS13 antibodies
Testing for binding anti-ADAMTS13 IgG antibodies should be considered every six months using an anti-ADAMTS13 ELISA that measures total IgG ADAMTS13-binding antibodies. Neutralizing-antibody testing should not be used in isolation.
3. Obtain monitoring samples before ADAMTS13 replacement therapy
Monitoring should be performed before administration of ADAMTS13 replacement therapy and should be undertaken in all patients receiving treatment.
4. Support centralized reporting and international learning
IWG TTP supports centralized reporting of cTTP cases in which ADAMTS13 antibodies develop during treatment. A coordinated approach can facilitate shared learning, additional investigation in expert laboratories, and appropriate reporting to regulatory authorities.
Building a Coordinated International Approach
Recombinant ADAMTS13 represents an important advance in the treatment of congenital TTP. As experience with this therapy grows, international collaboration will be essential to better understand uncommon findings, improve surveillance strategies, and ensure that emerging information can be evaluated collectively.
The IWG TTP will continue bringing together clinicians and investigators from around the world to share experience, evaluate new evidence, and develop coordinated approaches to important scientific and clinical questions in TTP.
Read the full IWG TTP letter:
[Download the July 2026 Monitoring Proposal]
This document reflects a proposal developed through IWG TTP discussion and should not be interpreted as a formal clinical practice guideline. Clinical decisions should be individualized by the treating healthcare team.