Lorcaserin

Lorcaserin (APD-356, expected trade name Lorqess ) is a weight-loss drug developed by Arena Pharmaceuticals. It has serotonergic properties and acts as an anorectic. On 22 December 2009 a New Drug Application (NDA) was submitted to the Food and Drug Administration (FDA) in the United States and lorcaserin is pending approval. On 16 September, an FDA advisory panel voted to recommend against approval of the drug based on concerns over both safety and efficacy. In October 2010, the FDA stated that it that it could not approve the application for lorcaserin in its present form.

Mechanism of action
Lorcaserin is a selective 5-HT2C receptor agonist, and in vitro testing of the drug showed reasonable selectivity for 5-HT2C over other related targets. 5-HT2C receptors are located almost exclusively in the brain, and can be found in the choroid plexus, cortex, hippocampus, cerebellum, amygdala, thalamus, and hypothalamus. The activation of 5-HT2C receptors in the hypothalamus is supposed to activate proopiomelanocortin (POMC) production and consequently promote weight loss through satiety. This hypothesis is supported by clinical trials and other studies. While it is generally thought that 5-HT2C receptors help to regulate appetite as well as mood, and endocrine secretion, the exact mechanism of appetite regulation is not yet known. Lorcaserin has shown 100:1 affinity for 5-HT2C versus other receptors.

Phase IIb and other early clinical trial results
Arena states that "[d]ata from Phase 2 clinical trials of lorcaserin demonstrated that patients who received the drug experienced significantly greater weight loss than patients who received placebo." At the end of 12 weeks, the groups which were administered lorcaserin lost an average of 4.0 pounds (10 mg/day), 5.7 pounds (15 mg/day), and 7.9 pounds (20 mg/day). The placebo group lost an average of 0.7 pounds, despite the fact that all groups received no diet or exercise instruction.

Upon discontinuation of lorcaserin treatment, lost weight is regained. In Phase 2 clinical trials, patients were tracked for 2 weeks post trial completion, and all groups regained weight more rapidly than they had lost. In pre-clinical trial studies, the weight of rats returned to control levels.

Phase III clinical trials
The Lorcaserin Phase III program consists of three different Phase III trials, BLOSSOM (Behavioral modification and LOrcaserin Second Study for Obesity Management), BLOOM (Behavioral modification and Lorcaserin for Overweight and Obesity Management), and BLOOM-DM (Diabetes Management).

BLOOM
BLOOM top line results were released on 30 March 2009. Measurements of efficacy using an intention to treat – last observation carried forward (ITT-LOCF), analysis showed that 47.5% of lorcaserin patients lost at least 5% of their body weight, compared to 20.3% for placebo. This result satisfies one of two alternate efficacy benchmarks in the most recent FDA draft guidance, which provides that a weight-management product can be considered effective if after one year of treatment the proportion of subjects who lose greater than or equal to 5% of baseline body weight in the active-product group is at least 35%, is approximately double the proportion in the placebo-treated group, and the difference between groups is statistically significant.

Additionally, 22.6% of lorcaserin patients lost at least 10% of their body weight, compared to 7.7% for placebo. Lorcaserin patients achieved an average weight loss of 5.8% of their body weight, or 12.7 pounds, compared to 2.2%, or 4.7 pounds, for placebo. Among the most frequent adverse events reported with lorcaserin were headache, dizziness, and nausea.

BLOSSOM
BLOSSOM results were released on September 18, 2009. Measurements of efficacy using an intent-to-treat last observation carried forward, or ITT-LOCF, analysis showed that 47.2% of lorcaserin patients lost at least 5% of their body weight, compared to 25.0% for placebo. Lorcaserin patients achieved an average weight loss of 5.9%, or 12.7 pounds, compared to 2.8%, or 6.3 pounds, for placebo.

BLOOM-DM
This trial examined the effect of lorcaserin in patients with diabetes mellitus. It was scheduled to end in May 2010. , no results are available.

Time schedule
Lorcaserin had a Prescription Drug User Fee Act (PDUFA) date of 22 October 2010. On 16 September 2010, a federal advisory committee voted against recommending approval for lorcaserin. In their 9-5 vote, the committee had raised concerns about the safety of the drug, particularly the findings of tumors in rats.

On 23 October 2010, the FDA decided not to approve the drug based on the available data. This was not only because of cancer promoting properties could not be ruled out, but also because the weight loss efficacy was "marginal".

Side effects
Generally, lorcaserin was shown in phase III testing to be a mild and tolerable agent. Trial participants found lorcaserin about as tolerable as placebo, with 7% of participants in both the lorcaserin drug and placebo arms dropping out due to side effects. Lorcaserin had the lowest discontinuation rates due to adverse events of any obesity drug in a phase III trial, as compared to discontinuation rates due to adverse events for bupropion/naltrexone (26% vs 13% for placebo), phentermine/topiramate (18% vs 9% for placebo), orlistat (7% vs 4% for placebo), sibutramine (9% vs 9%) and rimonabant (15% vs 7%).

Lorcaserin produced side effects in human clinical trials, but at rates not significantly different than placebo and mostly with mild and transient severity. The most common side effect was headache, experienced by about 18% of drug arm participants compared to 11% of placebo participants. Headache was the only reported side effect to occur at a frequency greater than 5 percentage points above placebo. Other reported side effects and their rates for lorcaserin and placebo patients, respectively, were as follows: upper respiratory tract infection (14.8% vs. 11.9%), nasopharyngitis (13.4% vs. 12.0%), sinusitis (7.2% vs. 8.2%) and nausea (7.5% vs. 5.4%). Adverse events of depression, anxiety and suicidal ideation were infrequent and were reported at a similar rate in each treatment group.

On 15 September 2010 it was reported by national news-media that lorcaserin was associated with the development of cancer in laboratory rats.

Echocardiograms for valvulopathy
Regarding the risk of cardiac fibrosis, Arena Pharmaceuticals sought to rule out an increase in the rate of valvulopathy of 20% or more because a number of anorectic drugs have been withdrawn for cardiovascular side-effects. In agreement with the FDA, Arena conducted regular and multiple echocardiograms of the phase III participants. At the 3, 6, and 12-month interval, the echocardiograms of participants of the BLOOM trial did not show any significant increase in valvulopathy over baseline, so the independent Echocardiographic Data Safety Monitoring Board (EDSMB) hired to monitor the trial allowed the trial to continue to the end. BLOOM participants received 18- and 24-month follow-up echocardiograms, but these results will not be reviewed by an EDSMB. The two other Phase 3 trials provide multiple and regular echocardiograms but they were not be reviewed by an EDSMB. BLOOM participants were pre-screened to exclude valvulopathy, but BLOSSOM and BLOOM-DM participants were not. Like BLOOM, BLOSSOM showed no significant increase in valvulopathy.

Rates of new FDA-defined valvulopathy in BLOOM were as follows: lorcaserin 10 mg twice daily (2.7%) and placebo (2.3%) at Week 52 and lorcaserin 10 mg twice daily (2.6%) and placebo (2.7%) at Week 104. For BLOSSOM, rates of new FDA-defined valvulopathy in BLOSSOM at Week 52 were as follows: lorcaserin 10 mg twice daily (2.0%), 10 mg once daily (1.4%) and placebo (2.0%).

Chemical properties
Lorcaserin is a benzazepine with a structure similar to dexfenfluramine, an anorectic drug that was withdrawn because of cardiovascular side-effects.

Financial aspects
In 2010, Arena Pharmaceuticals attended multiple biotechnology and pharmaceutical conferences and hosted several conference calls to discuss the Phase III results released so far. Market reaction to these results has been confused, driving it to a high of over $7 in early 2009 to a low of $2.61 in mid 2010. While management has reiterated its desire to partner lorcaserin with a large pharmaceutical company, in 2010 it has twice raised money from private hands, raising a total of nearly $60 million. For the first time, management has discussed the possibility of a go-it-alone strategy. Piper Jaffray has forecast lorcaserin sales of $3 billion in 2015. Arena has a very close financial relationship a group of private funds under the Deerfield umbrella name (Deerfield Private Design Fund, L.P., Deerfield Private Design International, L.P., Deerfield Partners, L.P., Deerfield International Limited, Deerfield Special Situations Fund, L.P., and Deerfield Special Situations Fund International Limited) under which Deerfield has lent Arena $100 million, purchased 11 million shares, and holds 28 million warrants to purchase additional shares at prices ranging from $3.23 to $5.48. On 15 September 2010 shares of Arena fell nearly 40%, from $6.85 to $4.13, on news that the lorcaserin has been linked to formation of malignant tumors in rats. On 16 September, an FDA advisory panel voted 9 to 5 to recommend against approval of the drug based on concerns over both safety and efficacy, trading on Arena's stock was stopped on that date, but after hours, the stock price fell about 40 percent.