(Reuters) - They may be difficult to pronounce, but pharmaceutical companies eager to grab the attention of doctors and patients are returning to drug names starting with X and Z.
Recent X-branded names include prostate cancer treatment Xtandi, lung cancer drug Xalkori, and Xgeva for cancer that has spread to bone. The letter Z is also becoming popular for new drugs like Zaltrap for colon cancer, melanoma drug Zelboraf and prostate cancer treatment Zytiga.
"The X and Z trend was pretty hot and heavy eight or nine years ago - that's when we had names like Zoloft, Zyban and Zocor," said Vince Budd, senior vice president at brand consulting firm Addison Whitney's healthcare division, referring to popular drugs for depression and high cholesterol.
"It was seen as an opportunity to create something unique," said Budd. "I believe we have come full circle and we are back there again, especially in oncology."
Of the 15 drugs with "X" appellations approved by the Food and Drug Administration since 1995, seven were launched in the last two and half years.
Marketing and linguistics experts say the rarity of X and Z in most words make for memorable, unique names. They are also "fricative" letters that imply speed or fluidity.
"In terms of cognitive psychology ... they need a memorable, distinctive name that doesn't have negative associations," said Matthew Traxler, psychology and linguistics professor at the University of California, Davis. "They may be distinct in terms of sound, but also visually distinct."
There are more practical reasons for the names.
The U.S. Food and Drug Administration as well as the European health regulator both have strict guidelines, not always overlapping, for what would be an acceptable name for a new medicine.
"You can't have a name look like or sound like another drug," said Scott Piergrossi, vice president, creative at Brand Institute Inc. "Someone could receive the wrong drug."
The concern extends to potential handwriting errors.
"Regulators want a lot of pen strokes up and down that provide a much more unique-looking name. It is more readable or interpretable if it has a lot of those letters," said Brannon Cashion, Addison Whitney's president.
Whether anyone can actually pronounce the name is of less concern.
"It's really about the novelty of the name," Piergrossi said. "Sometimes we get clients that can't pronounce names that start with X. Usually it creates a 'Z' sound."
Since patients rarely choose their drugs - at least those for serious diseases - drugmakers see the need to tailor names to a more narrow audience than general consumers.
"They are all going to be coined words," said Addison Whitney's Cashion. "Whoever creates the word basically defines how it is to be pronounced."
That is a much different strategy than you would see for a more consumer oriented drug product, such as Allergan Inc's eyelash-builder Latisse.
"Latisse is a more direct-to-consumer name. Patients will ask for it," Piergrossi said. "It is a coined form of Mattisse with "La" for lash. It is an image-driven, evocative name."
For a cancer drug, the main target audience is oncologists or medical professionals. "A pharma company may want to emphasize the drug's mechanism of action," Budd said.
Piergrossi said Xeljanz, a new Pfizer Inc drug for rheumatoid arthritis, is a great example of both innovative and practical naming forces at work.
"It includes both X and Z ... and the name is really key to the product profile," the Brand Institute executive said, explaining that the drug is designed to work by selectively blocking molecules known as Janus kinases. "For a doctor who is anticipating this product, when they see that JAN that might be the light bulb."
(Reporting By Deena Beasley in Los Angeles; Editing by Tim Dobbyn)