XYTOS Comparison of Photodynamic Therapy (PDT) using previous photosensitizers and XyChloro Photodynamic Therapy (XPDT) using XyChloro®, the new photosensitizer developed by the XYTOS Doctors.

The many positive results using PDT have been achieved with existing approved photosensitizers. XYTOS introduces XyChloro®, a newer more advanced agent. XyChloro® offers many advantages over existing photosensitizers such as better selectivity in cancer cells, significantly less toxicity, oral administration which translates into a very non-invasive treatment and rapid elimination or clearance from healthy cells which results in dramatically reduced periods of photosensitisation. These significant advances with XyChloro® permit the light therapy to be delivered to large areas of the body with the use of a patented 'CLT Light Delivery System'. With XyChloro® the XYTOS Doctors have dramatically increased the effectiveness of Photodynamic Therapy (PDT) for numerous types of cancers and have successfully transformed (PDT) from a localized treatment to a 'whole body' therapy.

The XYTOS Doctors developed XyChloro® addressing the following points which makes a good photosensitizer agent.

Non Toxic --- Amphyphylic -- Selectivity -- Rapid Clearance Time from Healthy Cells
Peaks of Absorption -- Depth of Penetration -- Singlet Oxygen Yield
Active with Ambient Light

The comparison results of the XyChloro® photosensitizers are detailed below and clearly show a dramatic increase in the productivity of XyChloro® over previous photosensitizers.

XyChloro® is a next generation photosensitizers that demonstrates our increasing commitment to eliminate cancer and offer our patients a better quality of life.
The sensitizers we use for XPDT have the following properties:

• Rapid clearance from healthy cells, but remain for some days in cancer cells.
• High concentrations in cancer cells, but negligible concentrations in healthy cells.
• Non-toxicity, with a wide safety margin between the therapeutic dose and the dose causing any toxic effects.
• Efficient production of free radical oxygen, the chemical species that attacks the (cancer) cells they are in.
• Increased penetration depth, activation in the red and infra-red regions, where the body is reasonably transparent to light (for XPDT)
• XyChloro treatment, as opposed to local treatment. This is only possible with XyChloro® a highly selective photosensitizers.
• Water soluble, so that it dissolves in the blood, but sufficiently lipophilic (fat loving) so that it can bind to cell membranes and pass into the cell.
• Greater understanding of mechanisms of action3,10

Comparison of safety (LD10)

Comment on Toxicity

XyChloro® is derived from chlorophyll, a significant component of our diet which is obviously not toxic. Standard toxicity testing shows that XyChloro® has very low toxicity as shown in the chart above. XyChloro® is considered to be a food to the body.

Comparison of clearance times from
Healthy Tissue

XyChloro Hours 24-48Photofrin Days 30-90Foscan Days 30

This chart also shows the number of cancerous cells (Purple) that absorb the photosensitizer in comparison to the number of healthy cells (Blue) that absorb the photosensitizer. As detailed in other sections of this website the photosensitizer has a positive charge and is considered a foodstuff to healthy cells. Because healthy cells also have a positive charge the photosensitizer rapidly clears from these cells within 24 to 48 hours (as shown above). Cancerous cells are negatively charged which attract the positively charged photosensitizer. These cancerous cells then can be treated with the light therapy and sound therapy, which will result in apoptosis for the cancerous cells. In previous photosensitizers healthy cell were affected in significantly larger numbers as referenced above and the photosensitizer was slow in clearing the body which resulted in a number of side effects including sensitivity to light. Thus the patient was unable to subject their body to light (i.e. the sun) for one to three months.

Solubility

Rapid Clearance Time (in days)

Depth of Penetration

Peaks of Absorption

Table above: Comparisons between XyChloro® which uses the core component chlorophyllin a product of chlorophyll and the earlier generation photosensitizers Photofrin and Foscan

Notes:

1. All three absorb in the red (630,635 and 650 nm). XyChloro® also absorbs in the infrared (865 nm), where the body is more transparent to light.
2. Absorption at 865 nm allows much greater penetration. Penetration data for Foscan is not known.
3. The XYTOS newest treatment procedure using XyChloro® utilizes a new white lights delivery system which covers all ranges of the spectrum.
4. Singlet oxygen yield. The percentage of incident light that gets converted to singlet oxygen, the agent that attacks the (cancer) cells. The higher the better.

Singlet Oxygen Yield

As shown there are a number of limitations with earlier photosensitizers

• Photosensitivity (extreme sensitivity to sunlight) because of slow clearance of the photosensitizer from healthy cells
• Inadequate selectivity for cancer cells, making PDT only a local therapy. Whole body therapy would result in excessive damage to healthy cells.
• Not enough free radicals are produced, i.e. the cancer cell killing capacity is limited;
• Activation at light wavelengths where the body is not very transparent, making it in effective with deep tumors.