Do Drug Companies Have an Obligation?

It was recently reported the Pfizer discovered that their drug, Enbrel, an anti-inflammatory used to treat rheumatoid arthritis ,appeared to lower the risk of Alzheimer's disease by 64%. This is a staggering number, especially when you consider that there are over 6 million people in the US diagnosed with this disease and that this number increases every day. With no cure, no prevention, and no reversal drugs currently available, doesn't it seem like a large pharmaceutical would leap at the opportunity to have a powerful effect on the lives of so many?
Instead, Pfizer decided not to release their findings. In fact, as quoted from the Washington Post, "Enbrel could potentially safely prevent, treat, and slow progression of Alzheimer's disease." However, a clinical trial would cost at least $80 million, and so the subject was dropped. It is one thing to decide that the trial was just too expensive; it is quite another to have the research available and refuse to release it, to just stay quiet about this potential miracle.
Does Pfizer have a moral obligation, an ethical responsibility to release their information? With 500,000 new diagnoses of Alzheimer's disease every year it just seems right to share this remarkable discovery with other scientists and drug companies. Perhaps because Enbrel's patent is expiring soon the company did not see the possibilities of profits, even against the capital outlay for clinical trials. I'd guess that they would have reaped billions had they worked to uncover a cure.
Should someone fearing Alzheimer's disease begin taking Enbrel? Currently there is not enough evidence to support beginning this drug regime, however, at the very least, I hope Pfizer will reveal all of their research findings so that a cure for this dreadful disease can be found.