The process of developing a drug from start to finish is incredibly arduous, usually involves around $1 billion in costs, and can take upwards of a decade to complete. To boot, a vast majority of drug hopefuls are destined to fail. That's why yesterday's news from Pfizer (PFE -2.09%) and the Food and Drug Administration should get breast cancer sufferers' blood pumping.

What's behind the "breakthrough" designation
The FDA yesterday gave Pfizer's Palbociclib the extremely rare and relatively new "breakthrough therapy" designation based on its phenomenal mid-stage trial results and the life-threatening nature of some of the cancers it could eventually treat.

The "breakthrough therapy" designation is about three months old -- it was a designation added to the Food and Drug Administration Safety and Innovation Act last year -- and is targeted at expediting experimental drugs through the development and review process. According to FDASIA, a breakthrough therapy is one that, "treat a serious or life-threatening condition, and preliminary clinical evidence indicates that the drug [or combination of drugs] may demonstrate substantial improvement over existing therapies on one or more clinically significant endpoints."

Very few breakthrough therapies have been approved up to this point -- then again, we're only working with about 100 days for the Food and Drug Administration to have assigned such a designation. Vertex Pharmaceuticals' received the first two "breakthrough therapy" designations from the FDA for two cystic fibrosis treatments, of which both involve the use of the already FDA-approved Kalydeco. The more intriguing "breakthrough therapy" designation is Pharmacyclics' (NASDAQ: PCYC) Ibrutinib for the treatment of two rare blood cancers, which analysts feel could have a peak sales value of $5 billion if approved.

The awe-inspiring numbers behind the designation
The potential for Vertex's cystic fibrosis dynamic duo and Pharmacyclics' Ibrutinib in clinical trials so far cannot be refuted, but I don't believe they hold a candle to the ridiculously strong clinical data that Pfizer's combination of Palbociclib and Novartis' (NVS -0.63%) Femara brought to the table in its mid-stage metastatic breast cancer trial.

The decision to assign the "breakthrough therapy" designation had to do with the end results, which showed Femara by itself providing trial patients with 7.5 months of progression-free survival, or PFS, while the combination of Palbociclib and Femara more than tripled that level to 26.1 months of PFS. I read that and my jaw hit the floor! That is the precise definition of a breakthrough drug that, if safe in trials, should be ushered through the development and review process with the utmost urgency.

Palbociclib itself targets ER+, HER2-positive breast cancer (the most common form of breast cancer) and works by inhibiting two cyclin dependent kinases, or CDKs, 4 and 6. These CDKs are essential for cell replication and their suppression has been demonstrated to interfere with tumor cell progression in advanced stages of the disease. Analysts at both Leerink Swan and JPMorgan estimate that, if approved for multiple indications, Palbociclib could have sales of $5 billion, annually.

A moat of competition, but plenty of upside
However, investors would probably be wise not to get too carried away with yesterday's news given that another therapy -- which I would certainly call revolutionary -- known as Kadcyla for HER2-positive breast cancer was just approved in February. Kadcyla, developed by Roche and ImmunoGen (IMGN) piggybacks a toxin on an antibody and, using ImmunoGen's proprietary targeted antibody payload technology, delivers a higher dose of toxin directly to the targeted cancer, which has a signature protein that causes the release of the toxin from the antibody. In late-stage trials, Kadcyla improved PFS by 50% over the placebo to 9.6 months.

Where Palbociclib will have a major one-up on the competition is in ease of use. It's an oral medication compared to Roche's Herceptin, Perjeta, or combo drug Kadcyla, which are all administered intravenously. Only the combination of Roche's Xeloda and GlaxoSmithKline's (GSK 0.28%) Tykerb is currently administered in pill form, but many newly approved drugs and pipeline products have shown PFS advantages over that combination. Even Palbociclib (going strictly off phase 3 results) whooped Kadcyla on a numerical PFS basis, but I'd like to see a head-to-head trial before I'd go making any definitive "one's better than the other" statements.

If Pfizer and Novartis can demonstrate that its combination is safe, I don't think there's a thing that'll hold back an accelerated approval within the next two years. Breast cancer patients definitely have a reason to celebrate if Palbociclib's 248% PFS improvement over the placebo holds true in further studies.