Demystifying Research for Medical and Healthcare Students. John L. AndersonЧитать онлайн книгу.
1 oncology trials are usually conducted using people who have cancer, and who have had all the treatments that are available, but which do not help anymore. They usually have to have a life expectancy of at least three months – so that they can be complete the trial (Arkenau et al. 2008). They are not usually paid for taking part, unlike non‐cancer clinical trial participants. The trials can involve a large commitment, both in terms of time, travel, and discomfort.
One of the dangers of taking part in a Phase 1 trial in the hope of finding a last‐minute, miracle cure is the therapeutic misconception – the belief that they are receiving treatment to help ‘cure’ their cancer. Thus, the way in which trial doctors explain the purpose of the trial and what they will go through has been subject of concern and they has been subjected to a lot of scrutiny. People with such advanced cancers have little hope of a miraculous cure. Sure, there is always that one grain of hope that there will be a trial of a new wonder drug which might save their lives – and no one would want to take any hope away. But we should not raise their expectations unduly. On the plus side, participants do get a lot of attention when they are on the trials. They are monitored carefully and anything significant can be communicated to their GP or Oncologist. They have something to hope for – and this can be very important to some people. However, like many of the chemotherapies which many participants would have been on in the past, there can be quite serious, even life‐threatening, side effects of the agents they are given. It is a big commitment and I have every respect for those who say ‘I am doing it for the benefit of others’.
One team published a paper in 2008, summarising the results of 29 Phase 1 trials at the Marsden Hospital in London. They analysed the outcomes of 212 patients who took part in these trials. Arkenau et al. describe them thus:
A total of 148 patients (70%) were treated in ‘first in human trials’ involving biological agents (132 patients ) or new cytotoxic compounds (16 patients ) alone and 64 patients (30%) received chemotherapy‐based regimens with or without biological agents.
I have highlighted their use of the terms ‘patients’ and ‘treated’. (This type of terminology was common when Rachel Ballinger and I did our analysis of communication between trial doctors and potential trial participants – I shall describe this later in Chapter 14) These terms perpetuate the therapeutic misconception – ‘I am still a patient being treated’.
Arkenau et al. evaluated the tumours before the third cycle of the trial – between weeks 6 and 8. They reported a ‘partial response’ in 19 people (9.4%), stable disease in 88 people (44%), and progression of disease in 95 (47%). ‘The 30‐ and 90‐day mortality was 1.9% (4 out of 212) and 18.3% (39 out of 212), respectively. Treatment related mortality was 0.47% (1 out of 212) and 11.8% (25 out of 212) of the patients have been withdrawn from an ongoing study due to toxicity’ (Arkenau et al. 2008). So, half a percent of people died because of the effects of the trial agents (or ‘treatments’ as they were described). They concluded:
This analysis demonstrated that treatment within the context of a phase I trial could be considered as a valuable therapeutic option. Interestingly, those trials incorporating classical cytotoxics were associated with a better outcome. Clearly, this relates to patient selection, particularly when the trial may involve the use of a cytotoxic in chemonaive cases. The treatment in our cohort was generally well tolerated and treatment‐related deaths and toxicities were low. Moreover, a significant number of patients achieved disease control for a significant duration. However, the challenge remains in appropriate patient selection and for this, the use of an objective clinical score could be a helpful tool.
(Arkenau et al. 2008)
Now, here is a challenge for you: (i) What sense do you make of these findings? (ii) What is missing from these trials? (My thoughts are given at the end of the chapter.)
Phase II Clinical Trials
If Phase I trials show that a new agent is relatively safe, the next step in the development of a new drug is a Phase II trial. These specifically check effectiveness – to see if it does what we want it to do. But these trials continue to monitor the safety and side effects of the developing treatment. Larger numbers are recruited into these trials. The CRUK literature defines them like this:
Phase II trials aim to find out:
if the new treatment works well enough to be tested in a larger Phase III trial;
which types of cancer the treatment works for;
more about side effects and how to manage them;
more about the best dose to use.
These treatments have been tested in Phase I trials, but may still have side effects that the doctors don't know about. Treatments can affect people in different ways.
Phase II trials are usually larger than phase I. There may be up to 100 or so people taking part. Sometimes in a phase II trial, a new treatment is compared with another treatment already in use, or with a dummy drug (placebo).
Some Phase II trials are randomised. This means the researchers put the people taking part into treatment groups at random.
(CRUK 2020)
Again, the principles are the same for cancer drug trials as for other drug trials except that cancer drug trials usually recruit people with cancer and do not pay them; whereas, in other drug trials, healthy volunteers are recruited to take part and they are paid.
Safety in Clinical Trials
There have been some tragic events during Phase I and Phase II trials. Some have been noted above in relation to Phase I oncology trials. But other trials involving heathy volunteers have ended in tragedy. I have selected a few to illustrate this.
TGN 1412 Trial
Six healthy young male volunteers at a contract research organisation were enrolled in the first Phase I clinical trial of TGN1412, a novel superagonist anti‐CD28 monoclonal antibody that directly stimulates T cells. Within 90 minutes after receiving a single intravenous dose of the drug, all six volunteers had a systemic inflammatory response characterised by a rapid induction of proinflammatory cytokines and accompanied by headache, myalgias, nausea, diarrhoea, erythema, vasodilatation, and hypotension. Within 12–16 hours after infusion, they became critically ill, with pulmonary infiltrates and lung injury, renal failure, and disseminated intravascular coagulation. Severe and unexpected depletion of lymphocytes and monocytes occurred within 24 hours after infusion. All six patients were transferred to the care of the authors at an intensive care unit at a public hospital, where they received intensive cardiopulmonary support (including dialysis), high‐dose methylprednisolone, and an anti‐interleukin‐2 receptor antagonist antibody. Prolonged cardiovascular shock and acute respiratory distress syndrome developed in two patients, who required intensive organ support for 8 and 16 days. Despite evidence of the multiple cytokine‐release syndrome, all six patients survived. Documentation of the clinical course occurring over the 30 days after infusion offers insight into the systemic inflammatory response syndrome in the absence of contaminating pathogens, endotoxin, or underlying disease. (Suntharalingam et al. 2006)
Fialuridine
Before it was trialled on human subjects, Fialuridine was tested on animals, including mice, rats, dogs, monkeys, and woodchucks. Those tests found that animals could survive doses which were a hundred times more than those given to humans without any toxic reactions. A Phase II trial on human subjects was conducted. In week 13 one of the subjects suddenly developed hepatic toxicity and lactic acidosis.