 Press ReleasesJuly 2007 Scrip Photopharmica targets infected wounds with its photodynamic therapy Photopharmica, a UK company spun out from the University of Leeds, has reported promising proof-of-concept data with its lead candidate PPA 904, a novel photodynamic therapy, for the treatment of microbial disease in wounds. The 32 patient Phase II study, which the company claims is the first ever for a topical photodynamic therapy (PDT), found that a single treatment significantly reduced the bacterial load of chronic leg and diabetic foot ulcers by around 90% compared with placebo (p=0.0017). Photopharmica said that PDT could bypass problems with resistance to antibiotics. The product also has good selectivity for bacteria versus host tissue, as it is taken up more quickly by bacteria than healthy tissue, meaning that healthy tissue is not also killed, a major concern in PDT. It is also easy to scale up and manufacture. The company plans to start a Phase IIb or III trial of the product by the end of the next year. Photopharmica said it was too early to give more details, but does plan to give multiple doses, although exactly how many is yet to be determined. PDT uses small molecules that are activated by light to kill diseased tissues or bacteria. PPA 904, a member of the phenothiazinium family of photosensitisers, is applied topically to infected areas (for around 15 minutes) and then activated by red spectrum light. Other therapies are sensitive to both blue and red light, but red light penetrates tissues more easily, said Professor Stan Brown of the University of Leeds, Photopharmica's chief scientific officer. Light energy is taken in by the drug and activates oxygen in the body to singlet oxygen - this activated form of oxygen, which is not free radical, is what kills the target cells. The drug acts in a similar way to catalyst, as oxygen cannot be activated directly by light. Another company. Activated Oxygen, markets products using another form of activated oxygen, O3 or ozone, to eradicate MRSA infection in wounds - a "bag" is placed over the wound and a mixture of ozone and oxygen is delivered to the infected area. It also produces ozonated gels and oils. There are several PDTs available, but they are only indicated in cancer, and include Photocure's Metvix, which is approved in the EU for non-melanoma skin cancer, and Axcan Pharma's Photofrin, which is available in the US and EU for bladder and oesophageal cancers. However PPA 904 is the leading antimicrobial PDT candidate, although there are several others in early preclinical development. Professor Brown said that the main advantage of PPA 904 is its broad-spectrum efficacy against both Gram-positive and negative bacteria - most others PDTs in early development are only effective against Gram-positive strains, he added. In the Phase II trial, PPA 904 was found to kill several types of bacterial species, including meticillin-resistant staphylococcus aureus (MRSA). The data also suggest that it could have a positive impact on ulcer healing: four of eight patients on PPA 904 in the leg ulcer group had completely healed within three months versus one of the eight in the placebo group. Professor Brown said that the study was not powered to show a significant difference in healing, and that this was only seen in a small number of patients, but added that the finding was promising and the firm would follow this up. The compound was well tolerated, and no treatment - related adverse events were reported. In May the intellectual property commercialisation company IP Group invested ?5.5 million in cash and shares in Photopharmica, and now has a 51.5% stake in the company. Photopharmica is also developing another antimicrobial agent, PPA 905, and a PDT candidate in cancer - both are in preclinical development. > menu |
