1 Drug That Could Reshape Breast Cancer Treatment

BioMarin (BMRN 2.87%) isn't as well known as other drugmakers, but you'll probably hear a lot more about the company as it advances its breast and ovarian cancer treatment, BMN-673, into phase 3 trials.

Over the weekend, BioMarin presented updated phase 1/2 data for the poly ADP-ribose polymerase, or PARP, inhibitor for the treatment of metastatic breast and ovarian cancer. The data showed a 50% response rate for patients treated with the drug.

The success in treating breast and ovarian cancer prompted BioMarin to move BMN-673 into phase 3, where it will study the drug as a monotherapy against a range of competing treatment options for those with locally advanced or metastatic breast cancer. The drug will specifically be studied as a treatment for patients with a particular BRCA mutation associated with breast cancer.

BRCA's connection to breast and ovarian cancer
BioMarin is targeting a mutation of the BRCA1 gene and BRCA2 gene. The mutation of those genes is identified through a genetic blood or saliva test, using the BRACAnalysis test made by Myriad Genetics (MYGN 0.59%). The BRACAnalysis was used in BioMarin's phase 1/2 trial and will be used in the phase 3 trial, too. 

The BRCA1 and 2 genes produce proteins that suppress tumors by repairing damaged DNA. They play an important role in keeping cells healthy. However, if either of these genes is mutated, cell damage can't be repaired and cancer can develop.

As a result, women inheriting the BRCA mutation have a significantly increased risk of breast cancer. Overall BRCA mutations account for 20%-25% of hereditary breast cancers and 5%-10% of all breast cancers.

The need for effective treatment is significant. 12% of women will develop breast cancer in their lifetime. That risk jumps to 45%-65% of all women when the BRCA mutation is present. Since those with the BRCA mutation have a higher risk of second cancers, and the prognosis is sometimes worse, some patients opt for bilateral mastectomy.

The incidence rates for ovarian cancer with the BRCA mutation are similarly worrisome. Roughly 1.4% of all women will be diagnosed with ovarian cancer in their lifetime, but that jumps to 11%-39% of women when the BRCA mutation is present. As a result, effectively identifying those with the BRCA mutation using Myriad's test, and then treating those patients with BioMarin's drug, may prove a significant advancement in treating these cancers.

Many competitors vying for space
The previous generation of chemotherapy drugs includes cisplatin, which was approved in 1978 as the drug Platinol, and tamoxifen, which is prescribed in both pre- and post-menopausal women to block estrogen from receptors in cancer cells.

Eli Lilly's (LLY 1.96%) Evista, an osteoporosis drug that blocks estrogen in breast tissue, is used to treat some post-menstrual patients. However, it's only used as preventative therapy and doesn't work in patients already diagnosed with invasive breast cancer. U.S. sales of Evista totaled $201 million in the second quarter, up 1.9% from a year ago. Lilly had hoped another drug, ramucirumab, would offer a more effective treatment. However, in late September the company reported that the drug failed to delay disease progression and hadn't improved survival.

Celgene's (CELG) Abraxane is another treatment option. Abraxane was approved as a breast cancer treatment in 2005 and has also recently been approved for non small cell lung cancer and pancreatic cancer patients. Celgene hopes to expand Abraxane's label across other indications, suggesting that the drug may have peak sales opportunity much higher than the $155 million it generated in the second quarter.

Roche has arguably the deepest bench of treatment options. In a phase 3 study of HER2 positive breast cancer patients -- a form of cancer accounting for 20% of breast cancers -- Roche's Kadcyla, which gained FDA approval in February, doubled the time patients lived without their disease progressing. The antibody-drug conjugate also showed a 47% reduction in the risk of disease worsening or death. Combined with sales of Roche's blockbuster breast cancer treatment Herceptin, and the more recently launched Perjeta, Roche generated $2.68 billion in breast cancer related drug sales in the second quarter. That number is likely to go higher given that Perjeta received approval as the first non-surgical pre-treatment for HER2 positive patients in September. Roche hopes Perjeta and Kadcyla will help offset generic risk once Herceptin loses patent protection in Europe next year and the U.S. in four years.

Novartis (NVS 2.27%) also hopes to win breast cancer prescriptions with Affinitor, which can be used to treat HER2-negative patients. However, the U.K. balked at pricing after reviewing data suggesting that while Affinitor delays progression, it doesn't offer a significant increase in survival. GlaxoSmithKline's Tyverb met a similar fate in 2012. Tyverb most recently failed to achieve endpoints as a treatment in gastric cancer, and the company pulled an FDA application for expanded use of Tyverb in breast cancer last year after speaking with the FDA and learning there were question marks that couldn't be answered by existing data. Tyverb generated $362 million in sales last year.

A Fool's final take
BioMarin has four commercialized drugs that combined to generate $136.8 million in second-quarter sales. While those sales were 10% higher year-over-year, the eventual market for BMN-673 would conceivably dwarf current revenue. As a result, Fools should watch the drug's progression through phase 3 closely. While biotech companies have significant risks and often fail in trials, a successful phase 3 could mean that BMN-673 has potential to significantly boost the company's revenue.