Let's take a look at three stocks -- CTI BioPharma (NASDAQ:CTIC), Agenus (NASDAQ:AGEN), and Salix Pharmaceuticals (UNKNOWN:SLXP.DL) -- which are all climbing higher in pre-market trading this Tuesday morning.

CTI BioPharma climbs after completing enrollment in a late-stage trial
CTI BioPharma (formerly known as Cell Therapeutics) is up 7% in pre-market trading this morning, after the company completed enrollment in its PERSIST-1 Phase 3 clinical trial for pacritinib, an oral JAK2/FLT3 inhibitor being evaluated as a treatment for myelofibrosis. Myelofibrosis, a bone marrow disease which disrupts the production of red blood cells, causes bone marrow scarring, severe anemia, an enlarged spleen and liver, and chronic fatigue.

There are approximately 320 patients enrolled in the trial, which will compare the safety and efficacy of pacritinib against other available therapies. The primary endpoint is for a percentage of patients to achieve a 35% or more reduction in spleen volume after 24 weeks of treatment. PERSIST-1 is one of two phase 3 trials for the drug, which are intended to support a New Drug Application (NDA) in the U.S. by late 2015, followed by a Marketing Authorization Application (MAA) in Europe in 2016.

CTI will receive a $20 million milestone payment from its commercialization partner Baxter International (NYSE:BAX) when the last patient in the trial begins dosing this quarter. If pacritinib is approved, CTI and Baxter will share U.S. profits equally, and CTI will receive royalties on net sales overseas. Roth Capital Partners believes that pacritinib has peak sales potential of $750 million based on approvals for myelofibrosis and other blood disorders.

CTI has one approved product, the lymphoma treatment Pixuvri, which generated revenue of $2.3 million in 2013. CTI expects the drug to eventually generate peak sales of $240 million based on its EU sales alone. The majority of CTI's revenue of $34.7 million in 2013 came its pacritinib partnership with Baxter, which has a potential value of $172 million. 

Agenus soars on positive mid-stage data for brain tumor treatment
Shares of Agenus are up 21% in pre-market trading after the company reported positive results from its phase 2 trial evaluating its Prophage cancer vaccine in patients with newly diagnosed glioblastoma multiforme (GBM), a common type of malignant brain tumor.

For the study of 46 patients, 33% were alive at 24 months. Patients dosed with Prophage demonstrated a median overall survival rate of approximately 24 months.

The median progression free survival rate was nearly 18 months -- twice to three times as long as patients treated with radiation therapy and temozolomide, an oral chemotherapy drug. 22% of patients were alive without any progression at 24 months.

Agenus does not have any approved products. Its pipeline consists of three categories of treatments -- a vaccine adjuvant, heat shock protein vaccines, and checkpoint antibodies. Its QS-21 Stimulon Adjuvant has attracted the most attention, and is currently in various mid to late-stage trials to boost the effectiveness of vaccines from GlaxoSmithKline, Pfizer, and Johnson & Johnson.

If Prophage is approved, analysts at Global Hunter Securities expect peak sales potential of $1 billion on its GBM indication alone -- which would be a huge boost for this clinical-stage biotech.

Salix surges on positive late-stage results for rifaximin
Last but not least, Salix Pharmaceuticals is up 11% in pre-market trading after it announced positive data from its TARGET 3 phase 3 trial evaluating Xifaxan (rifaximin) TID (three times daily) as a treatment for irritable bowel syndrome with diarrhea (IBS-D).

The treatment was administered for 14 days, after which a statistically significant proportion of rifaximin-treated subjects responded to the treatment when compared to a placebo. The composite primary endpoint of the trial consisted of a reduction in IBS-related abdominal pain and improvement in stool consistency during the 4-week treatment-free follow-up period.

Three types of doses of rifaximin are currently being tested for IBS-D, Crohn's disease, and the prevention of complications with early decompensated liver cirrhosis. Of these, the IBS-D indication is the most advanced in clinical trials.

Xifaxan, which is currently approved for traveller's diarrhea and hepatic encephalopathy, is the most important of Salix's six approved drugs. Last year, sales of Xifaxan rose 25% year-over-year to $645.6 million, accounting for 69% of Salix's top line. Analysts at Leerink Swann believe that Xifaxan could eventually generate peak sales of $1.6 billion by 2018 if approved for IBS-D and other indications.