In short
Iopofosine (131I), also known as CLR 131, is an investigational radiopharmaceutical being studied in Waldenstrom macroglobulinemia, a rare type of B-cell lymphoma. One Phase 2 trial (NCT02952508) is evaluating the major response rate in 65 patients who have received at least two prior lines of therapy. The trial is currently authorised and uses a single intravenous infusion of the study drug.
Key points
- Iopofosine (131I) is an investigational radiopharmaceutical also known as CLR 131.
- It is being studied in Waldenstrom macroglobulinemia, a rare B-cell malignancy.
- The single registered trial is a Phase 2 study with 65 participants.
- The trial is currently authorised and investigates a single intravenous infusion.
- The primary endpoint is the major response rate (MRR) up to 12 months after infusion.
- Eligible patients must have received at least two prior lines of therapy.
What is iopofosine (131I)?
Iopofosine (131I) is an investigational radiopharmaceutical. Its full chemical name is 18-(p-iodophenyl)octadecyl phosphocholine, and it is also known by the development code CLR 131. A radiopharmaceutical is a drug that contains a radioactive substance and is used for diagnostic or therapeutic purposes. Iopofosine (131I) contains the radioactive isotope iodine-131, which delivers radiation to target cells. The substance has no marketing authorisation in the records available and remains an investigational medicine.
How does iopofosine (131I) work?
As a radiopharmaceutical, iopofosine (131I) combines a targeting molecule with the radioactive isotope iodine-131. The phosphocholine part of the molecule is designed to be taken up by certain cancer cells, particularly those of B-cell malignancies. Once inside or near the cancer cells, the iodine-131 emits radiation that damages the cells. The trial record describes the substance as a drug given by intravenous infusion, but does not provide a detailed molecular mechanism of action.
Which conditions is iopofosine (131I) studied for?
The registered clinical trial investigates iopofosine (131I) in one condition:
- Waldenstrom macroglobulinemia — a rare, slow-growing type of non-Hodgkin lymphoma that affects B cells and leads to an overproduction of an abnormal antibody called IgM. The trial focuses on patients whose disease has returned after or not responded to previous treatment.
How is iopofosine (131I) given?
In the registered trial, iopofosine (131I) is given as a single intravenous infusion at a dose of 15 millicuries (mCi). A millicurie is a unit used to measure radioactivity. The trial also includes potassium iodide given orally at a dose of 130 milligrams. Potassium iodide is not the studied substance; it is used to protect the thyroid gland from radioactive iodine.
What do the clinical trials show?
One Phase 2 trial, NCT02952508, is registered for iopofosine (131I) in Waldenstrom macroglobulinemia. The trial is interventional and is currently authorised, meaning it has received regulatory approval to proceed. It plans to enrol 65 participants. The study is part of a larger programme called CLOVER-1, with an expansion part specifically for Waldenstrom macroglobulinemia called CLOVER-WaM.
The primary endpoint is the major response rate (MRR). This is defined as the proportion of patients who achieve a complete response, a very good partial response, or a partial response, measured using criteria modified from the VIth Waldenstrom Macroglobulinemia Criteria for Response Assessment. Responses are assessed up to 12 months after the first infusion of iopofosine (131I).
Who can take part in these trials?
The trial enrols patients with Waldenstrom macroglobulinemia who have received at least two prior lines of therapy. A line of therapy is a course of treatment given for a disease; when one treatment stops working or causes unacceptable side effects, a new line of therapy begins. This means the study focuses on patients whose disease has already been treated with at least two different treatment approaches.
What side effects are known?
The registry record for this trial does not list side effects. No supplementary sources on the safety profile of iopofosine (131I) are provided, so side effect information cannot be reported here.