DrugWatch

Cancer - hope or hype?

➜ Anthony Walker*

There have been many false dawns in the field of cancer vaccines, but some of the new products look distinctly promising.

sing vaccines that stimulate the hysteria, safety, selectivity and potency not by normal tissues. There are numer- immune system to fight cancer remain the hallmarks of a , and ous variants: subunit and anti-idiotype Uappeals to many as a natural cancer vaccines promise efficacy with vaccines and immuno-gene therapy to approach that is both safe and effective. limited – or no – side-effects. Serious name but three. Much effort has been And, judging from a recent headline adverse events have been the exception directed toward high-tech solutions in in the UK newspaper The Times in the clinical trials of experimental vac- this area, but it has become apparent – “Vaccine jab could cure ” – cines conducted to date. At the same that tumours continue to mutate as the there is clear public interest in this area. time, there have been few glimpses of disease progresses, evading the immune Even big pharma is showing signs of real benefit, with numerous false dawns system by downregulating or losing the excitement. At a partnering conference and much disappointment. expression of the target antigen. one of the more traditional majors said But there was an explosion of interest in The third group, multivalent and ultra- cancer vaccines had moved from the ‘no this field after the unravelling of mech- valent vaccines, combine several anti- strategic interest’ category to ‘watchful anisms for triggering cytotoxic T-cell gens in one formulation to overcome waiting’ – an almost seismic shift to (CTL) response about 15 years ago. immunological evasion. This is akin to those of us who remember past scepti- It was a fundamental breakthrough in combination chemotherapies, whereby cism. But is there promise beyond the immunology that provided insights into resistance to one element is mitigated hype? And can vaccines find a place in the workings of the immune system and by the presence of others. Taking this modern cancer therapy? how to activate and direct it to attack concept still further, a number of vac- The immune system has always played cancers. Moreover, our knowledge of cines use inactivated whole cancer cells an important role in cancer prevention. how cancers, in turn, deploy defence because they contain the entire spec- Pre-malignancies, induced by toxic mechanisms to evade or disable the trum of tumour antigens in an ultrava- chemicals, excessive exposure to UV immune system has also increased. lent formulation. radiation, viral infection or simply Cancer vaccines can be divided into spontaneous genetic mutations, arise three categories. The first group, non- CELL VACCINES at intervals throughout the body. They specific immunostimulants, covers the The most encouraging results so far are generally detected and destroyed agents BCG, interleukin-2 and interfer- have come from cell vaccines. These by a panoply of immune mechanisms, on alpha, which are used to treat blad- have moved the state of the art beyond mostly before we are aware that any- der cancer, renal cell carcinoma and safety and immunogenicity into the thing untoward has happened. On rare malignant . They boost levels realm of clear clinical benefit. Indeed, occasions, this occurs after the clinical of activity in the immune system to in 70 recently published vaccine trials, manifestation of cancer, resulting in reverse immunosuppression induced by half used cell therapies (late-stage clini- spontaneous regressions. Vaccine the tumour, resulting in rejection of the cal highlights are shown in the box). treatment aims to harness these mech- cancer. Although many agents have Broadly speaking, there are two types of anisms in a therapeutic setting. been tested, few have been successful cell vaccine: patient-tailored (autolo- The prospect of avoiding the severe and these failures have tarnished the gous) and off-the-shelf (allogeneic). The side-effects associated with many treat- entire field. autologous approach involves harvesting ments underpins the demand for can- Specific-target vaccines are based on patients’ tumour and immune cells, pro- cer vaccines. Despite recurrent vaccine the antigens expressed by tumours but cessing them ex vivo to induce immuno-

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logical activity and then returning them times as there may be with certain NEXT STEPS to the donor. Companies using auto- autologous systems). The field of cancer vaccines has logous tumour cells include German The leading proponent of this approach matured considerably over the past few firm LipoNova, California-based Cell is Dr Donald Morton, founder of years. Several products are in Phase III Genesys, Avax Technologies from CancerVax and a pioneer in clinical trials with the prospect of potential Kansas and Intracel from Maryland. cancer for more than product registrations over the next 18 to From a scientific standpoint, autolo- four decades. CancerVax’s lead product, 24 months. If all goes to plan, vaccines gous cell vaccines have significant Canvaxin, is composed of three human could be available to patients in 2006 or merit, matching the tumour antigens melanoma cell lines rendered replica- 2007. precisely to the patient being treated. tion-incompetent through irradiation, Although significant challenges and They have also produced favourable with BCG used as a vaccine adjuvant risks remain – as they will until the first results in trials of several cancers. But for the initial two doses. Canvaxin, is registered – these interest in this approach has waned which is currently in two international have shifted away from the early proof- because of inherent logistical difficul- randomised Phase III trials in malig- of-concept issues towards the practical ties and the associated high costs. nant melanoma, has arguably produced realities of manufacturing and regula- The other autologous technology employs better safety and clinical efficacy data tory affairs. patients’ immune cells. Dendreon, IDM than those supporting the approval of This, together with compelling data from Paris, France, Merix from North several new cancer therapies. from late-stage trials, is convincing the Carolina and Geron, based in California, Other companies active in this area sector that cancer vaccines represent use dendritic cells (DCs), whereas Xcyte include Cell Genesys (which also has much more than hype. and Targeted Genetics, both of Seattle, autologous-vaccine programmes) and Washington, use T-cells. Again, this London-based Onyvax, whose lead *Anthony Walker is CEO of Onyvax, a London- approach is scientifically and medically product for prostate cancer, Onyvax-P, based biotechnology company which develops novel sound, but doubts remain as to whether is in Phase II trials, data from which will cancer therapies that harness the body’s immune the treatments can be applied across be reported later this year. system. broad patient populations. Allogeneic cell vaccines rely on the can- cer antigens present in a high percent- RECENT TRIAL RESULTS age of tumour types. Although the spec- trum of tumour-specific and tumour- RCC Vaccine (LipoNova). The renal-cell carcinoma vaccine was tested in a 55-centre, 558- associated antigens (TSAs and TAAs patient trial. At 70 months, progression-free survival rates were 72% in the vaccine group respectively) will be unique to a tumour and 59.3% in the control group. The product was well tolerated, with only 12 adverse events deposit, some cell lines express tens if associated with the treatment. not hundreds of common antigens at Canvaxin (CancerVax). In a sample of 263 patients who underwent complete resection of high frequency. When immortalised, clinically detectable stage IV melanoma, 150 people received post-surgical treatment with these cell lines can be used in vaccines. Canvaxin in Phase II protocols and 113 received other or no adjuvant therapy. Median over- They grow indefinitely in culture sys- all survival and five-year overall survival were significantly increased in patients who received tems and can be manufactured at indus- the treatment vaccine compared with those who didn’t (36 compared with 18 months, and trial scale in modern cGMP facilities. 39% compared with 19%). Another advantage of allogeneic cell Provenge (Dendreon). In a randomised Phase II/III trial in hormone refractory prostate can- vaccines is that the concept behind cer, patients receiving Provenge had a significant survival advantage, with an 89% average them – they are a product in a bottle overall increase in survival time compared with the placebo group. Median survival time in rather than a bespoke service – is famil- the treatment group was 30.1 months compared with 22.3 months among people who were iar to the pharma industry. Furthermore, not treated. At 30 months from randomisation, the survival rate for Provenge-treated patients the costs are lower from economies of was 3.7 times higher than for those receiving placebo. scale and, importantly, they are readily available (there are no lengthy lead

This article was first published in Scrip Magazine, May 2004 (134, 6-7). Reproduced by permission of PJB Publications Ltd.

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