A trial looking at taselisib and tamoxifen for breast cancer that has spread (POSEIDON)

You may be able to join the trial if all of the following apply.

• You have breast cancer that has spread to another part of your body, or your cancer has grown into surrounding tissue but can’t be removed with surgery
• You have breast cancer that is very sensitive to oestrogen (oestrogen receptor positive ) or to progesterone (or both)
• You have breast cancer that is HER2 negative
• Your cancer came back or got worse while you were taking hormone therapy such as anastrazole or exemestane
• The trial team are able to take a new sample (a biopsy ) from the cancer in your breast or can use a sample that was taken when you had surgery or a biopsy in the past
• You are well enough to be up and about for at least half the day (performance status 0, 1 or 2)
• You have satisfactory blood test results
• You are willing to use reliable contraception during the trial and for 2 months afterwards, if there is any chance that you could become pregnant
• You are at least 18 years old

As well as the above, you may join the 2nd part of the trial if the following also apply.

• Your cancer can be seen on a scan
• If you are having types of drugs called bisphosphonates , you must have been taking them for at least a month

You cannot take part in the trial if any of the following apply. You

• Have cancer that has spread to the brain or spinal cord unless it has been successfully treated and you don’t need to take steroids
• Have had hormone therapy in the last 2 weeks
• Have had chemotherapy in the last 3 weeks (6 weeks if you had chemotherapy drugs called nitrosoureas or mitomycin C)
• Have had more than 5 types of chemotherapy for advanced breast cancer
• Have had radiotherapy  in the last 2 weeks
• Have had monoclonal antibody treatment in the last 4 weeks
• Have had major surgery in the last month
• Have had any other cancer in the last 5 years apart from non melanoma skin cancer or a very early stage of cancer called carcinoma in situ  that has been successfully treated
• Have not recovered from side effects of other drugs apart from hair loss or tingling in your hands and feet (peripheral neuropathy)
• Have a problem with your stomach or bowel that could affect how you absorb tablets
• Have a long term infection
• Have certain heart problems (the trial team can advise you about this)
• Have diabetes and you take medication everyday
• Take steroids on a long term basis
• Have a problem with the way your blood clots unless you are having a drug such as warfarin, rivaroxabane or low dose heprarin to control this
• Are known to be sensitive to any of the drugs in this trial
• Are known to have HIV
• Are pregnant or breastfeeding

As well as the above, you cannot join the 2nd part of the trial if any of the following apply

• You have had drugs called PI3K inhibitors, AKT inhibitors, PDK inhibitors or mTOR inhibitors (your doctor can tell you more about this)
• You have had tamoxifen in the past, unless you had it after your surgery for breast cancer to try to stop your cancer coming back and you stopped taking it more than a year before your cancer started to spread
• Your cancer suddenly gets worse and you need to have chemotherapy