UPDATE 2-US FDA: Lip data on Medicis shot may be unreliable

* FDA staff cites small sample size, no comparison

* Medicis shares down 1 percent (Adds trial details, sales expectations)

By Esha Dey

WASHINGTON, April 25 (Reuters) - Data on the effectiveness of Medicis Pharmaceutical Corp's (MRX.N) wrinkle-filler Restylane as a lip plumper may be unreliable, U.S. drug reviewers said in documents released on Monday ahead of an advisory panel meeting to discuss the merits of the treatment.

U.S. Food and Drug Administration staff cited concerns that included the lack of a control arm in study data that would help compare the drug's efficacy with a placebo or a rival treatment, the small number of patients studied and the use of a non-validated scale to assess the drug's effectiveness.

The reviewers also expressed concern on whether the safety and effectiveness of Restylane for lip augmentation was adequately tested in people of color.

Restylane is already approved to fill out facial wrinkles, such as laugh lines, and is also used off-label to augment and contour lips.

The safety outcomes of the lip trials were consistent with the pivotal study that led to the drug's facial wrinkle approval.

Medicis performed three studies that tested the drug's use as a lip plumper -- a study with 120 patients and two smaller trials with 20 and 21 patients.

Restylane is an injectable gel composed of hyaluronic acid, which holds onto water in the skin, purified from a Streptococcus species of bacteria.

Medicis, which had $700 million in revenue in 2010, is a specialty pharmaceutical company focused on aesthetic and dermatological products, and generic drugs.

An FDA approval is not expected to significantly boost sales, given that lip augmentation is a small market and the drug is already being used off-label, but it will allow the company to market the drug for the new use.

The company's other big aesthetic product, Dysport, is partnered with French drugmaker Ipsen (IPN.PA) and competes with Allergan Inc's (AGN.N) hugely popular wrinkle smoother Botox.

Beauty treatments like Botox and Restylane have become household names, with Botox bringing in sales of $1.42 billion in 2010. While Botox is usually used to smooth out wrinkles and lines around the eye area, Restylane is more often used on the lower part of the face, around the mouth.

An FDA panel of independent experts will vote on Restylane's use as a lip filler on Wednesday.

Restylane is being taken to the advisory panel since dermal filler injection for lip augmentation is a first-of-the-kind indication, the reviewers said.

Medicis shares were down 1 percent to $34.72 in Monday afternoon trading on the New York Stock Exchange. (Reporting by Esha Dey; Editing by Tim Dobbyn)