As far as I can make out the relationship between PFS and OS varies by cancer types and even patient groups within cancer types. So the whole gambit of combinations are possible.
For women in first remission PRR argue that they are a unusual group and the positive PFS results shown in the SOC group will not translate to OS improvement. With respect to this argument I will believe it when I see it.
For women in second remission a PFS advantage was seen in the Cvac group. The theory is that this will translate to a OS advantage. This is why Can-004(2) was changed to second remission and OS as the primary outcome.
By my reckoning Prima has not produced a positive clinical trial result in quite a long while. And the sentiment on this forum, the share price and market interest reflects this sad state of affairs.
The hope now is that Can-003 gives a signal for OS. If it does it builds confidence in the outcome for Can-004(2).
Lets look at the happy situation of where one of these cancer vaccines has been approved.
The efficacy data for Provenge (which PRR uses as a template) that was used to gain approval was summarised as follows.
“In a series of 3 phase III trials with almost identical design, sipuleucel-T was compared to placebo. The first 2 trials utilized time to progression of disease as the primary outcome; neither showed a statistical difference between the treatment group and placebo. The third trial utilized overall survival as the primary outcome. In that trial, the median overall survival was statistically higher in the sipuleucel-T group with a hazard ratio for death of 0.78, a 22% relative risk reduction with an absolute increase of 4.2 months in overall survival.
Similar to the first two trials, the third trial did not show a difference in time to progression of disease and did not show any disease response or stabilization. These results are controversial. While it is common to have a tumor response without an effect on survival, it is uncommon to have no effect on objective response or progression free survival but to show an overall survival benefit. There may be other unknown prognostic variables affecting the results. “
So we can note a few things here. First it took many tries to get positive results ... and even now they are open to conjecture. Three P3 trials cost what? $60m or more. And it took a decade. But ultimately it was OS that won the day.
After the setback of Can-003, PRR is at the stage where it wants positive results for Can-004(2) as a proof of concept trial which will support someone (big pharma or retail investors) funding a P3 trial.
The power calculation for Can-004(2) is based on achieving sufficient confidence in success in P3 that is higher than current percentage of oncology P3 positive trial outcomes. In other words if Can-004(2) is positive big pharma is able to calculate the odds of success in P3. And lay down their bets accordingly.
Now that is some time down the track. What PRR need now is a positive OS signal out of Can-003. Plain and simple.
On the conference issue. There are a few good reasons to release results at a prestigious conference. First there are independent experts on hand that can be encouraged to say encouraging things. Second the conference organisers arrage and can access the mainstream media to give wider publicity to your results. Third they have a level of “peer review”. which means they are not simply results spun by a company pr machines. People take notice of them.
I appreciate its not easy being glass half full with PRR. Its a shocker on many levels. Its possible my optimism that Can-003 OS can make a real impact here is completely wrong. PRR has wrong-footed me quite a bit. QRX is another one of my favourites that has completely got me stumped. And after PBT today ... maybe its best just to be honest here and say ... haven’t got a clue.
Southoz
PRR Price at posting:
3.9¢ Sentiment: Buy Disclosure: Not Held
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