BOSTON ( TheStreet) -- Scientists are making great strides toward developing new tests enabling the early diagnosis of Alzheimer's disease, perhaps even before patients start exhibiting the loss of memory and cognitive function that are the terrible hallmarks of the neuro-degenerative disease.

Coming up with drugs to effectively treat or even reverse Alzheimer's is proving to be much a more elusive goal, unfortunately.

Tuesday's announcement by Eli Lilly ( LLY) that Alzheimer's patients treated with its experimental drug semagacestat were performing worse than placebo patients in two late-stage studies. (forcing Lilly to stop the studies) was just the latest in a string of negative results from Alzheimer's drug trials.

Other recent Alzheimer's late-stage drug study failures have tripped up the partnership between Pfizer ( PFE) and Medivation ( MDVN), Myriad Genetics ( MYGN) and the now-defunct Neurochem. A drug owned by Elan ( ELN) and Wyeth (since bought by Johnson& Johnson ( JNJ)) and another controlled by Elan and Transition Therapeutics ( TTHI) are being studied in ongoing phase III studies despite what might be optimistically called mixed phase II results.

Long term, recently announced breakthroughs involving new brain imaging techniques and the discovery of biomarkers for Alzheimer's might allow scientists to learn more about the causes of Alzheimer's. Along with new diagnostics, the scientific consensus seems to be moving towards designing clinical trials that target patients in early-stage Alzheimer's patients, or even patients with pre-Alzheimer's, which may give drugs a better chance for success.

Meantime, drug companies forge ahead with Alzheimer's clinical trials. Perhaps one of the drugs listed below will succeed where so many others have failed. After Tuesday's bad news from Lilly, investors seeking Alzheimer's gold could use some cheering up.

Ten Alzheimer's Disease Drugs in Mid- to Late-Stage Clinical Trials:

Pfizer and Medivation
Drug: Dimebon
Drug type: Mitochondrial
Stage: Phase III
Dimebon failed a phase III monotherapy study that enrolled patients with mild to moderate Alzheimer's. An additional phase III study is still in progress: The "Concert" trial is studying the combination of Dimebon plus Aricept in patients with mild to moderate Alzheimers. Results are expected in 2012. Pfizer and Medivation are also conducting a phase III study of Dimebon in Huntington's disease, with results expected in the first half of 2011.

Johnson & Johnson (with minority partners Pfizer and Elan)
Drug: bapineuzumab
Drug type: Amyloid beta
Stage: Phase III
Lackluster data released in 2009 from a closely watched phase II study has cast a long shadow over bapineuzumab's development. Most recently, Johnson & Johnson said top-line results from pivotal, phase III studies in mild to moderate Alzheimer's patients wouldn't be ready until the end of 2012, a pushback from 2011.

Elan and Transition Therapeutics
Drug: ELND-005
Drug type: Amyloid beta
Stage: Phase II
On Aug. 9, Elan and Transition announced plans to move ELND-005 into phase III studies despite what appears to be mixed results from a recently completed phase II study in mild to moderate Alzheimer's patients. The phase II study of ELND-005 failed to meet its cognitive and functional endpoints overall but the companies said the drug had an effect on amyloid-beta proteins in the spinal fluid and showed some clinical benefit in a subgroup of patients.

Eli Lilly
Drug: Solanezumab
Drug type: Amyloid beta immunotherapy
Stage: Phase III
Two phase III studies of solanezumab are currently enrolling patients with mild to moderate Alzheimer's patients. Results are expected in 2012-2013.

Bristol-Myers Squibb ( BMY)
Drug: BMS-708163
Drug type: Gamma secretase inhibitor
Stage: Phase II
BMS-708163 belongs to the same class of gamma secretase inhibitors as Lilly's discontinued drug semagacestat. Top-line results from the ongoing phase II study of '708163 in patients with mild to moderate Alzheimer's are expected in the fourth quarter.

Baxter ( BAX)
Drug: Gammagard
Drug type: Amyloid Beta
Stage: Phase III
Baxter expects to complete enrollment in the phase III Gammagard study by the end of the year, with results likely in 2012. The phase III study hopes to confirm positive results seen in phase II studies of Gammagard.

Prana Biotechnology ( PRAN)
Drug: PBT2
Drug type: Metal ions
Stage: Phase II
Prana has announced, but not yet started, a large phase IIb study of PBT2 in mild to moderate Alzheimer's patients to bolster an early signal of efficacy seen in a smaller phase IIa study.

AstraZeneca ( AZN) and Targacept ( TRGT)
Drug: AZD1446
Drug type: Nicotinic Acetylcholine Receptors
Stage: Phase II
A small (54 patient) phase II study of AZD1445 in combination with Aricept began in early 2010 with top-line data expected in late 2010 or early 2011.

Roche
Drug: RG3487
Drug type: Nicotinic Acetylcholine Receptors
Stage: Phase II
A phase II study combining RGB3487 with Aricept completed patient enrollment in the second quarter.

GlaxoSmithKline ( GSK)
Drug: Affitope AD02
Drug type: Amyloid beta immunotherapy
Stage: Phase II
Results from a phase II study could be ready in 2012.

List compiled with assistance from BioMedTracker

-- Reported by Adam Feuerstein in Boston.

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Adam Feuerstein writes regularly for TheStreet.com. In keeping with TSC's editorial policy, he doesn't own or short individual stocks, although he owns stock in TheStreet.com. He also doesn't invest in hedge funds or other private investment partnerships. Feuerstein appreciates your feedback; click here to send him an email.

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