Protherics PLC "Protherics" or the "Company"), the international biopharmaceutical company focused on critical care and cancer, today announces that the first patient has been enrolled in a phase 2a study of its Angiotensin Therapeutic Vaccine (ATV) for the treatment of hypertension.

Hypertension is a major risk factor for serious and common cardiovascular diseases such as heart attacks and strokes and the global market for anti-hypertensive therapies is estimated to be worth around US$30 billion*. The majority of existing therapies are tablets which need to be taken on a daily basis, usually for the rest of a patient's life. However, many patients with high blood pressure fail to take their medicines as prescribed, and it is estimated that approximately 70% of patients with hypertension do not have their blood pressure adequately controlled*. Therefore, a vaccine approach, which may require only three injections and a booster after six months rather than daily medication, should improve patient compliance with treatment.

The phase 2a, double-blind, placebo-controlled clinical study in 124 patients with mild to moderate hypertension has been initiated in the UK. Patients will be given a course of injections over six weeks. The study will assess the safety and tolerability of the vaccine, incorporating Protherics' promising novel vaccine adjuvant, CoVaccine HT™. In addition both antibody response and effect on blood pressure will be assessed. The blood pressure results are expected in the first half of 2009.

Protherics has shown in a previous phase 2a study that a formulation of ATV, incorporating the vaccine adjuvant Alhydrogel®, modulated key hormones involved in regulating blood pressure in hypertensive patients. A new formulation of ATV has now been developed, incorporating the CoVaccine HT™ adjuvant, which has demonstrated a much stronger immune response in pre-clinical models.

CoVaccine HT™ and ATV are protected by extensive patents and applications in the US, EU and the rest of the world. The first US patent on ATV was granted in May 2008.

Andrew Heath, Chief Executive of Protherics, commented:

"We are excited about the prospects for ATV, a potential value driver for the company. A vaccine approach to the treatment of high blood pressure promises to address the issue of poor patient compliance with daily medication and thus reduce the incidence of stroke and heart attacks. With data expected within a year, this could be a major outlicensing opportunity."

*Company estimates

About Protherics

Protherics (LSE: PTI, NASDAQ: PTIL) is a leading international biopharmaceutical company focused on specialist products for critical care and cancer.

Protherics has produced two FDA approved biologics for critical care use which are currently sold in the US: CroFab™, a North American pit viper antivenom and DigiFab™, a digoxin antidote. Protherics reported revenues of £26.1 million for its year ended 31 March 2008 and a strong cash balance of £37.7 million. The Company's strategy is to use the revenues generated from its marketed and out-licensed products to help fund the advancement of its broad, late stage pipeline.

Protherics has two major development opportunities in its portfolio. CytoFab™ is being developed by AstraZeneca, for the treatment of severe sepsis, following a major licensing deal announced in December 2005. AstraZeneca is conducting an additional phase 2 programme following changes to the commercial manufacturing process. A new formulation of Angiotensin Therapeutic Vaccine, for the treatment of hypertension, has today commenced a phase 2a study. Protherics also has four novel products being developed in a range of cancer indications where it intends to undertake the sales and marketing in the US and/or the EU.

With headquarters in London, the Company has approximately 300 employees across its operations in the UK, US and Australia.

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About Angiotensin Therapeutic Vaccine

Angiotensin Therapeutic Vaccine (ATV) is a conjugate vaccine containing a peptide analogue of the hormone angiotensin I cross linked to the carrier protein keyhole limpet haemocyanin (KLH). ATV is designed to treat hypertension by stimulating the immune system to neutralise angiotensin I, a peptide hormone that plays a key role in the regulation of blood pressure.

Protherics has previously shown in hypertensive patients that a first generation formulation of ATV modulates key hormones involved in regulating blood pressure. An improved formulation of ATV has now been developed, incorporating a novel vaccine adjuvant, CoVaccine HT™, which has shown evidence of stimulating a much stronger immune response in pre-clinical models. CoVaccine HT™ was acquired by in June 2006 by Protherics from CoVaccine BV.

A vaccine approach to the management of hypertension is expected to improve patient compliance with therapy, which is a major problem in achieving control of high blood pressure with current therapy. Because of its envisaged slow onset and sustained effect, ATV has the potential to be used on its own, or in combination with existing high blood pressure medications, to improve the control of hypertension. For more information, visit here.

About Hypertension

Hypertension is one of the most common medical conditions in developed countries and is a risk factor associated with heart attacks, heart failure, blood vessel problems and kidney damage. Current treatments are tablet based, requiring daily doses, often for life, and patient compliance is often poor. The pharmaceutical market for high blood pressure treatment is the largest single therapeutic sector in the world, with global sales exceeding US$30 billion per annum.

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