CAMBRIDGE, Mass. ( TheStreet) -- Ariad Pharmaceuticals ( ARIA) has been hit with a wave of selling in the past two weeks tied to investor concerns about the commercial launch of the company's leukemia drug Iclusig. The selling has erased all the gains made in the Ariad since the beginning of the year. For the past two weeks, Iclusig scripts have been soft, up 8% for the week ended March 8 and down 17% for the week ended March 15, according to IMS Health. Say what you will about the reliability and meaningfulness of a week's worth of prescription data, but Wall Street follows this stuff closely. A down week in scripts for a drug like Iclusig -- with high sales expectations already baked into Ariad's $3.4 billion market valuation -- raises alarm bells. Ariad shares have closed in the red for eight straight trading days -- a streak that finally appears to be ending Wednesday. Still, Ariad is down 17% during this time period. I spoke with a healthcare investor Wednesday who's short Ariad and believes the stock is still significantly over-valued because Iclusig's peak sales will never match current expectations. On average, analysts are projecting Iclusig sales to grow from $47 million in 2013 to $611million in 2016. According to this fund manager's checks with doctors, Iclusig is being prescribed primarily for the small percentage of chronic myeloid leukemia (CML) patients no longer treatable with first generation ( Novartis' ( NVS) Gleevec) and second-generation (Novartis' Tasigna and Bristol-Myers Squibb's ( BMY) Sprycel) drugs. The small number of CML patients with the T315I mutation -- specifically targeted by Iclusig -- are also receiving the drug. Ariad's efforts to position Iclusig as a first or second-line CML treatment -- necessary to capture enough market share to meet sales expectations -- are failing because of the drug's significant side effects, the fund manager believes. "Iclusig is a dirty drug. Patients get all of the toxicities of the competing CML drugs without any meaningful improvement in efficacy," he said. FDA approved Iclusig with a black box warning alerting doctors to watch for blood clots that have caused fatal heart attacks and strokes, and liver toxicity including reports of liver failure and death.