pipeline

In the book "The Code of Extraordinary mind" the author was talking about placebo effect, "half of all drugs that fail in late-stage trials drop out of the pipeline due to their inability to beat placebos." What's meant by pipeline here? production line?

The pipeline is the process that starts with the idea of a drug, goes through development (which may take years), test (including at least three stages of clinical trials), approval, and finally making it generally available. Many ideas enter the pipeline but few stay in it to the end. Specifically, one part of testing is to see if the new drug has better effects than a placebo (a drug with no medical benefit, such as a sugar pill, though placebos often help patients because of their psychological effects). This sentence says that many new drugs don't do better than placebos.

It's a variation of "in the pipeline", in the process of being provided or completed: Several projects are in the pipeline.
So the development of these drugs is halted [because they are no more efficient then the placebos.]