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How your Phase 2 or 3 trial can benefit from molecular imaging

Maarten Brom, PhD

There is about a 2/3rd chance that your clinical trial fails in Phase 2 or 3, the most time-consuming and expensive phases of drug development. Luckily, you can use molecular imaging to improve your chances of a successful outcome and increase operational efficiency.

The goal of Phase 2 and 3 studies.

The benefit of molecular imaging in early clinical development is that it gives you an indication of therapeutic efficacy. Even before Phase I. However, if you stuck to the traditional development process, (without imaging) it is likely you don’t have efficacy data at the start of your Phase 2 trial.

That’s why, in Phase 2 you investigate whether your drug has any efficacy in 100 to 300 patients. After a successful Phase 2 trial, you determine the efficacy of the new drug in a Phase 3 trial. These usually range from 300 to 3,000 patients.

A clinical trial is successful when your drug shows a therapeutic effect in a large proportion of your patients. Nevertheless, only one-third of Phase 2 clinical trials move successfully to Phase 3. So, what could be the reason? And how can molecular imaging help?

Molecular imaging for patient selection in late clinical development.

Your drug has a specific target that is present in diseased cells. However, the target is usually not expressed in all patients that have the disease. When the diseased tissue in a patient does not express the target, you will not observe a therapeutic effect. So, if a relatively large proportion of the patients do not express the target, you will find a low therapeutic effect in the patient population of your clinical trial. This will make you think that your drug does not work for that disease.

To avoid this misconception, you can use molecular imaging to determine whether the target is expressed in the patient. If the patient does not express the target, you simply do not include this patient in your clinical trial. This way you gather more accurate information on the therapeutic effect of your drug. Even more important, you do not terminate a potential new drug based on wrong efficacy data in a population with a limited degree of target expression.

Another advantage is that when you only include patients that express the target, your drug’s chance of success increases. As a result, you generally need less patients to show the therapeutic effect and success of your drug.

Molecular imaging of downstream therapeutic effect in Phase 2 and 3 trials.

The therapeutic effect of a new drug is usually based on clinical outcome measures (endpoints). For example, tumor shrinkage or survival for novel anti-cancer drugs. It can take time before you see improvement in clinical outcome measures, especially when you look at the overall survival.

Before improvement of disease progression can be seen, changes in downstream processes and metabolism after drug treatment can occur. You can use molecular imaging to show these changes shortly after initiation of the treatment with your new drug.

For example, a decrease in tumor glucose metabolism by FDG PET imaging (as a measure of decrease tumor viability). You can also use molecular imaging to measure a decrease of target expression after drug treatment.

As the benefit of molecular imaging in early phases of clinical development is clear, it can also be used in Phase 2 and 3 trials. Wondering what type of imaging best fits your stage of clinical development? Contact us here.

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