BTG plc (LSE:BGC), the life sciences company, announces that the full results of the US phase II safety study of Varisolve® are being presented today at the American College of Phlebology (ACP) 22nd Annual Congress. The results confirm that treatment with Varisolve® in subjects with right-to-left (R-L) cardiac shunts, which may allow residual bubbles following treatment to enter the cerebral arterial circulation, does not cause cerebral injury.

Principal investigator Kathleen Gibson, MD, of Lake Washington Vascular Surgeons, commented: "There is increasing interest in using foam sclerosant to treat varicose veins, because of the many benefits to patients including the speed of treatment and no requirement for general or tumescent anaesthesia. However, concerns have been raised relating to the potential risk of cerebral gas embolisation, particularly in patients who have a right-to-left cardiac shunt that may allow residual bubbles from the foam to enter the arterial circulation. This study found no evidence of any injury to the brain, retina or heart following treatment with the proprietary Varisolve® polidocanol microfoam in patients with cardiac shunts. These results should not be generalised to other foams, such as air-based foams that have high nitrogen content and are insoluble in blood."

Louise Makin, chief executive officer of BTG, said: "It was very important for the future development and commercial potential of Varisolve® to demonstrate no subclinical effects following treatment in the brains of people with a cardiac shunt. Having removed this uncertainty, we have been able to press ahead with confidence both with partnering discussions and with the pilot phase III trials, in anticipation of the pivotal phase III trials that are planned to begin around mid-2009."

Dr Gibson's oral presentation,Proprietary Polidocanol Endovenous Microfoam Bubble Embolization Does Not Cause Cerebral Injury, will describe the multi-centre phase II safety study. Eligible patients were screened for the presence of a R-L shunt and if positive were given a baseline diffusion-weighted brain MRI scan. Patients were then treated with Varisolve® and monitored for 60 minutes following treatment using Transcranial Doppler (TCD) to detect bubbles entering the middle cerebral artery (MCA). Additional safety evaluations included blood oximetry, cardiac markers and electrocardiograms. Patients with detected MCA bubbles had follow-up diffusion-weighted brain MRI scans 24 hours and 28 days after treatment, neurological and visual field examinations plus other routine assessments. The study objective was to treat and follow up 50 patients with detected MCA bubbles.

Of 82 patients treated, 73% (60) had detection of MCA bubbles and all had at least one post-treatment MRI. No new MRI lesions or abnormal findings in the neurological and visual field examinations were detected in any patients, and none had any evidence of cardiac ischaemia.

Sapheno-femoral junction reflux was eliminated in 94% of patients at one month, and 88% had occlusion of the great saphenous vein. Adverse events were generally mild and transient and were consistent with previous experience with Varisolve®.

In a second oral presentation at ACP entitled Neurological and Visual Symptoms Following Treatment of the Saphenous Veins with Two Formulations of Polidocanol Endovenous Microfoam, Janet Rush, MD, BTG's Head of US Regulatory & Medical Affairs, will describe the characteristics of the Varisolve® microfoam before and following its reformulation to minimise residual gas bubbles. Dr Rush will also compare clinical experience and results from studies of the original formulation (7% nitrogen) and the new formulation (0.01-0.8% nitrogen). She will conclude that of 534 patients treated with the original formulation, one patient (who had a cardiac shunt) had potentially clinically concerning neurological symptoms, while there have been no clinically concerning neurological or visual symptoms in any of the 106 patients treated with the new formulation.

A third oral presentation, by David Wright, MB, FRCS, BTG's Vice President of Medical Affairs, entitled A Single-Center Pilot Study of Polidocanol Endovenous Microfoam (PEM) Treatment to Evaluate Presence and Durability of Gas Emboli Using Echocardiography, will explore the relative echocardiographic appearances of the original and new formulations of Varisolve®, with the objective of determining whether nitrogen ingress can "stabilise" small bubbles thereby causing them to persist in the circulatory system. Twenty patients were randomised to receive treatment with the original or new formulation of Varisolve®, and 10 additional patients were also randomised to pre-breathe oxygen or not. This was to explore whether pre-breathing oxygen would de-nitrogenate the blood sufficiently to prevent any stabilisation of the bubbles that might occur.

Dr Wright will conclude that all patients receiving endovenous microfoam ablation treatment have right sided cardiac bubbles. He will also conclude that the echocardiographic appearance is unaltered by elimination of nitrogen, and that pre-breathing with oxygen does not change the presence of bubbles. Treatment of the varicose veins was successful with all 35 patients (including 5 training patients) having occlusion of the great saphenous vein and elimination of reflux at 28 days.

In addition to the oral presentations, Gregory Suplick, BTG's Vice President of Clinical Development, will present two poster presentations entitled Patient Recruitment Strategies and Referrals Associated with a Multicenter Phase II Study of Patients with GSV Incompetence and Patient Pre-Qualification Tools Used to Recruit Patients for a Multicenter Phase II Study of Patients with GSV Incompetence.

About BTG

BTG in-licenses, develops and commercialises pharmaceuticals and has a broad pipeline of development programmes targeting neurological and other disorders including varicose veins. The company also has a substantial and growing revenue stream of milestone payments and royalties from out-licensed products. BTG operates from offices in London, Philadelphia and Osaka.

BTG