Data from a small US trial of the TOOKAD VTP system in low-risk disease

Earlier this year we reported data from a randomized, 400-patient trial in Europe of TOOKAD® Soluble vascular targeted photodynamic therapy (VTP) with the proprietary drug WST11.

We also noted that this system had been approved for the treatment of prostate cancer in Mexico.

We now have data from a small, US-based, Phase I/II clinical trial of VTP hemiablation using the same system in just 30 patients. (We had reported on the initiation of this trial back in 2010. Apparently it has taken a considerable amount of time to enroll and treat enough patients … or maybe the manufacturer delayed publication of the data until they knew the results of the much larger European trial.)

Taneja et al. state, in an article in the Journal of Urology, that the patients enrolled in this small study were all diagnosed with “unilateral, low volume, Gleason 3 + 3” disease; they were treated at one of five enrolling centers; and they were evaluated by post-treatment MRIs and biopsies. Escalation of the treatment dose was permissible.

Note that the so-called “light dose index” or LDI is defined as the sum of the light fiber length ÷ the desired treatment volume.

The brief summary of the study’s results is as follows:

  • 21/30 men received optimized dosing of 4 mg/kg WST11 and 200 J energy (after dose escalation).
  • Residual prostate cancer on post-treatment biopsy was found
    • In the treated lobe in 10/21 patients
    • In the untreated lobe in 4/21 patients
    • In both lobes in 1/21 patients
  • When the LDI was ≥ 1, at optimal dosing, 11/15 patients (73.3 percent) had a negative post-treatment biopsy in the treated lobe.
  • Six men who underwent re-treatment, with optimal dose and LDI ≥ 1, also had negative post-treatment biopsies.
  • There were minimal effects on urinary function, sexual function, and overall quality of life.

Tanjeda et al. conclude that:

Hemiablation of the prostate with WST11 VTP was well-tolerated and resulted in negative biopsy in the treated lobe for the majority of men. Dosing parameters and LDI appear related to tissue response as determined by MRI and biopsy.

Of course data from a small, 30-patient trial won’t be sufficient to obtain an approval for the TOOKAD system here in the US. The question is likely to be whether the US Food and Drug Administration would accept data from the 400-patient European trial for the purposes of an approval or whether they will require a large, randomized trial here in the USA (similar to the one conducted in Europe).

The other questions are going to be: who really needs this type of treatment, and can we identify such patients with accuracy up front? Such a treatment clearly offers benefits for men with low-risk disease who simply can’t deal with the idea of active surveillance. Equally, it is unlikely to have any meaningful impact on the lifespan of any man with low-risk disease and a life expectancy of 15 years or less. Working out who will really benefit from a treatment like this may be a challenge.


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