Exhibit 99.1
 Alkermes Contacts:For Investors: Rebecca Peterson, (781) 609-6378For Media: Barbara Yates, (781) 258-6153
 ALKERMES PROVIDES OUTLOOK FOR ALKERMES PLC AND UPDATE ON
ADVANCING PRODUCT PORTFOLIO AT ANALYST AND INVESTOR DAY
  Portfolio of Five Major Products Driving Long-Term, Double-Digit Revenue Growth from New $450
Million Base 
   Launched in UK Triggering $7 Million Milestone to Alkermes 
  VIVITROL ® Net Sales of $9.7 Million in First Quarter Fiscal 2012 Reflecting 14%
Growth
Quarter-Over-Quarter 
  Pipeline Highlights Include Progress for Three Clinical Programs: ALKS 9070 to Enter Pivotal
Clinical Program for the Treatment of Schizophrenia by End of 2011; ALKS 37 Phase 2b Study
Initiated for Treatment of Opioid-Induced Constipation; and ALKS 5461 Phase 1b Topline Results in
Treatment-Resistant Depression Expected by End of 2011 
 WALTHAM, Mass., July 18, 2011
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Analyst and Investor Day Highlights
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    Financial Updates:Alkermes will provide expanded financial expectations for
Alkermes plc.
 
    
    Revenues:In fiscal year 2012, the company expects pro forma
revenues to grow at a single-digit rate to a range of $460 million to $480
million. Pro forma revenues of the combined companies on a trailing 12-month
basis as of March 31, 2011 were approximately $450 million. Revenue growth for
Alkermes plc will be driven by sales from five commercial products, each in
their product growth phase and with long patent lives: RISPERDAL®
CONSTA® (risperidone long-acting injection);
INVEGA® SUSTENNA® (paliperidone palmitate);
AMPYRA® (dalfampridine); VIVITROL and BYDUREON.




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
    
    Adjusted EBITDA:In fiscal year 2012, the company expects
Adjusted EBITDA margins in the 15% to 20% range yielding pro forma Adjusted
EBITDA in the range of $70 million to $90 million. In fiscal year 2013 and
beyond, Adjusted EBITDA margins are expected to expand to 30% to 35%.
    
    VIVITROL:Alkermes will announce that VIVITROL had net sales of
$9.7 million for the first quarter of fiscal 2012, an increase of 14% over the
previous quarter.
    
    BYDUREON:Alkermes will announce today that BYDUREON has been
launched in Europe, with the first commercial sale in the U.K. This triggers a
$7 million milestone payment to Alkermes, expected in the second quarter of
fiscal year 2012.
 
    
    Clinical Pipeline Updates:Alkermes will report several key advances of promising
products in its pipeline, including the following:
 
    
    ALKS 9070 to enter pivotal clinical program in schizophrenia:Alkermes
will provide details on the recently completed phase 1b study of ALKS 9070, a
proprietary molecule for the treatment of schizophrenia. ALKS 9070 is designed to
provide once-monthly dosing of a medication that converts in vivointo
aripiprazole, a molecule that is commercially available under the name
ABILIFY®. Alkermes will describe plans to advance ALKS 9070 into
pivotal clinical development by the end of calendar 2011.
    
    ALKS 37 advances into a phase 2b definitive, dose-ranging study for the
treatment of opioid-induced constipation (OIC):Alkermes will announce the
initiation of a phase 2b study of ALKS 37, an orally-active, peripherally
restricted opioid antagonist for the treatment of OIC. The multi-center,
randomized, double-blind, placebo-controlled, repeat-dose study is designed to
assess the safety, tolerability, efficacy and pharmacokinetic profile of ALKS 37 in
approximately 150 patients. According to IMS Health, an estimated 266




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million prescriptions were written for opioids in the United States during 2010, and
many studies indicate that a high percentage of patients receiving opioids are
likely to experience side effects affecting gastrointestinal motility. Alkermes
expects to provide topline results from the study mid-year calendar 2012.
    
    ALKS 5461 phase 1b topline results in treatment-resistant depression
(TRD) expected in 2011:Alkermes will provide details on the recently initiated
phase 1b study of ALKS 5461 in TRD, with the topline results of this study expected
by the end of calendar 2011. The company will describe ALKS 5461s mechanism of
action as a non-addictive antagonist of kappa opioid receptors, a promising
approach for the treatment of depression.
    
    Initiation of the VICTORY study:Alkermes will announce the initiation
of the VICTORY study (VIVITROLs Cost and Treatment
Outcomes RegistrY), an observational, open-label,
multi-center registry of approximately 500 opioid dependent patients treated with
VIVITROL. The study is designed to evaluate and describe characteristics of
patients receiving VIVITROL in real-world clinical practice; assess clinical,
health economic and health-related quality of life outcomes and provide additional
data to inform future research on VIVITROL. Data readouts from the study will be
reported on an ongoing basis.
 Webcast
  About Alkermes




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® ® ®
 Note Regarding Forward-Looking Statements




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Important Additional Information and Where to Find It
 www.sec.gov




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financial@alkermes.com www.alkermes.com
 Participants in Solicitation
  ® ® ® ® ®  ® ®
  
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    Adjusted EBITDA, a non-GAAP measure of
operating results, is defined as net income or loss plus or minus net interest
expense, provision for income taxes, depreciation and amortization of costs and
revenue, share-based compensation expense, legal settlement gain and other net
charges, including charges arising from this transaction. Adjusted EBITDA is
not presented as, and should not be considered an alternative measure of,
operating results or cash flows from operations, as determined in accordance
with U.S. GAAP. It is anticipated that Adjusted EBITDA will be used to
evaluate the operating performance of the combined business. Adjusted EBITDA,
as defined here, may not be comparable to similarly titled measures reported by
other companies.