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 such as 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 such as Zoloft, Zyban and Zocor," says Vince Budd, senior vice-president at US 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," says 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 past two-and-a-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," says Dr Matthew Traxler, psychology and linguistics professor at the University of California, Davis. "They may be distinct in terms of sound, but they are also visually distinct."

Error-proofing requirements

There are more practical reasons for the names.

The US 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," says Scott Piergrossi, vice-president, creative, at Brand Institute. "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," says 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 says. "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," says 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’s eyelash-builder Latisse.

"Latisse is a more direct-to-consumer name. Patients will ask for it," Piergrossi says. "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 emphasise the drug’s mechanism of action," Budd says.

Piergrossi says Xeljanz, a new Pfizer 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 says, 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."