PolyTherics Announces a Research Collaboration With Spirogen Ltd. to Develop Novel Antibody-Drug Conjugates for the Treatment of Cancer

London, UK, 2 April 2012 – PolyTherics Limited (“PolyTherics”), a provider of solutions to enable the development of better biopharmaceuticals, announces that it has formed a research collaboration with Spirogen Limited ("Spirogen"), a leading oncology-focused company developing DNA sequence-targeted agents, to develop antibody-drug conjugates (ADCs) that combine PolyTherics’ proprietary site-specific conjugation chemistry with Spirogen’s highly potent novel cytotoxic drugs to produce novel ADCs for the treatment of cancer.

Under the collaboration, the two companies will produce the ADCs using PolyTherics’ proprietary TheraPEG™ linker technology to site-specifically conjugate Spirogen’s potent pyrrolobenzodiazepines (“PBDs”) cytotoxic agents – known as warheads - to antibodies and antibody fragments. The companies will then test the potency of the resulting ADCs in preclinical models of cancer. PolyTherics and Spirogen will jointly seek partners to develop the most promising ADC candidates that arise from the collaboration.

John Burt, CEO of PolyTherics, commented, “This is an exciting opportunity to combine our validated conjugation technology with Spirogen’s potentially best-in-class PBD warheads. The novel antibody-drug conjugate reagents that we develop will have broad application for the development of ADCs as new cancer therapies.” Chris Martin, CEO of Spirogen, added, “We believe that ADCs will represent a significant medical breakthrough in cancer therapy over the coming decade, and that PolyTherics’ TheraPEG™ conjugation technology will broaden the applications where our PBD warheads and linkers can create highly potent potentially market-leading ADC candidates.”

About PolyTherics

PolyTherics is a private UK biotech company that provides technology solutions to enable the development of better biopharmaceuticals. PolyTherics has developed proprietary technologies for the site-specific conjugation of polymers, such as polyethylene glycol (PEG), to any therapeutic peptide or protein, including antibodies, antibody fragments and protein scaffolds. Its proprietary linker chemistry and novel reagents can be used to produce protein drug conjugates, targeted imaging agents, bispecific proteins, and more stable proteins and peptides with longer half-lives. Products developed using PolyTherics’ technologies have significant product quality and production advantages, including better pharmacokinetic and pharmacodynamic profiles, increased product homogeneity, consistency of manufacture and more cost-effective process economics. PolyTherics has licence agreements with Celtic Pharma and Nuron Biotech and expects products developed using its technologies to be in clinical development in the next 12-24 months. In January 2012, PolyTherics acquired Warwick Effect Polymers and extending the company’s offering to include low viscosity polymers, as an alternative to PEG, and glycopolymers for targeted drug delivery.

PolyTherics has raised over £7.5 million of private capital and is backed by a number of institutional investors, including Imperial Innovations (LON:IVO), Proven Health VCT plc, The Capital Fund, Advantage Enterprise and Innovation Fund, Mercia Funds 1 & 2, Oxford Technology VCT 3 plc and Oxford Technology 4 VCT plc, and a number of high net worth individuals with funds managed by Longbow Capital LLP.

For more information, please visit: www.polytherics.com.

About Antibody Drug Conjugates

ADCs are highly targeted drug constructs which combine monoclonal antibodies specific to particular types of tumor cells with potent cytotoxic agents (warheads). The antibodies bind to specific receptors (antigens) on the surface of the target cell. Once inside the target cell the cytotoxic agent is released, killing the cell directly. This minimizes the impact on normal, healthy tissues and significantly reduces the side effects associated with chemotherapy treatments. ADCs have extensive potential therapeutic applications in several disease areas, particularly in cancer. This is evidenced by the publication of very promising efficacy data by several pharmaceutical companies including Genentech, and the recent FDA approval of a novel anti-cancer ADC, Adcetris, developed by Seattle Genetics for the treatment of lymphomas. The principle can also be applied beyond antibodies, with the possibility of linking warheads to antibody fragments, peptides, vitamins and hormones.

About Spirogen Limited

Spirogen Limited (“Spirogen”) was founded in 2001 as a spin-out from several institutions including University College, London. It is majority owned by Celtic Therapeutics. It has developed a novel class of highly potent cytotoxic warheads based on its proprietary pyrrolobenzodiazepines (“PBD’s”), DNA minor groove binding agents, which bind and cross-link specific sites of DNA of the cancer cell. This blocks the cancer cells’ division without distorting its DNA helix, thus avoiding the common phenomenon of emergent drug resistance. In contrast, many cancer chemotherapeutics distort the structure of DNA resulting in the ability of the cancer cells to develop resistance to further therapy. Spirogen has been developing its PBD technology for more than ten years, including a standalone PBD agent already in an NCI-sponsored Phase II study in cisplatin resistant ovarian cancer. Its business model is to partner its technology with pharma and biotech for use in the development of novel drugs. It has a number of industry collaborations, including collaborations with Genentech announced in 2011 and with ADC Therapeutics announced in 2012. For more information, please visit: www.spirogen.com

For more information:

Tim Watson

College Hill

Tel: +44 (0)207 866 7861

Email: polytherics@collegehill.com

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