EXHIBIT 99.1
 
 For release at 6:30 a.m.
 Contacts:
 DUSA Pharmaceuticals Reports
First Quarter 2010 Corporate Highlights and Financial Results
 Q1 Domestic Kerastick ® Revenues up 33% year over year; Domestic PDT Revenues up 27%
Company generates $0.9 million in positive cash flow
 th
 WILMINGTON, Mass.  May 11, 2010 ® ®
 Highlights for the first quarter include:
 
    
    Total product revenues were $8.7 million for the quarter, representing a $1.6 million or
22% year-over-year improvement.
    
    Domestic PDT revenues totaled $8.0 million for the quarter, representing a $1.7 million
or 27% year-over-year improvement.
    
    Domestic Kerastick® revenues totaled $7.5 million for the quarter,
representing a $1.9 million or 33% year-over-year improvement.
    
    Kerastick® gross margins for the quarter matched a record high at 86%.
    
    The Company experienced significant bottom line improvement on both a GAAP and non-GAAP
basis for the quarter.
 
    
    GAAP net loss for the quarter was $0.4 million, representing a $1.2
million or 74% year-over-year improvement.
    
    The Company reached break-even on a non-GAAP basis for the quarter,
representing a $1.3 million year-over-year improvement.
 
    
    The Company generated $0.9 million in positive cash flow (change in cash and cash
equivalents and marketable securities) during the first quarter of 2010.
 Management Comments:




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® ®
  First Quarter 2010 Financial Results:
 ® ® ® ® ® ® ®
 ®
   Other Updates:
 
    
    The Company was recently advised that a receiver had been appointed for the laboratory
that it was using to perform analytical release testing and stability testing for its
Levulan® Kerastick® product due to non-payment of its bank loan.
As a result, this




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laboratory is no longer able to perform these services on an on-going basis. DUSA has engaged the services of a new laboratory and has successfully completed
the transfer of the technology and analytical test methods. On May 5, 2010, following
discussions with the FDA, the Company filed a 30-day Changes Being Effected (CBE-30)
supplement to validate the use of the new laboratory. The Company has sufficient
Kerastick® inventory on-hand to meet projected demand beyond June 4, 2010, the
end of the 30-day review period. If the FDA review process is delayed beyond our
expectations, we would likely experience a back order on our Levulan®
Kerastick® for a period of time, which would have a negative effect on our
revenues. The Company believes it is on schedule for a successful transition.
 
    
    On May 7, 2010, the Company announced that the United States Patent and Trademark
Office had issued a notice of allowance for a key new patent related to its proprietary
PDT light source, the BLU-U®, Blue Light Photodynamic Therapy Illuminator.
The new patent will have method of treatment claims which cover the use of DUSAs blue
light technology and aminolevulinic acid HCL (Levulan®) for the treatment of
actinic keratosis as well as the diagnosis and treatment of other disease states such as
acne, cancer, psoriasis and photodamaged skin. The patent also has claims that will
cover DUSAs blue light technology in conjunction with its proprietary
Levulan® Kerastick® formulation of aminolevulinic acid HCL. The
patent, once issued, which is scheduled to occur on May 25, 2010, will cover our approved
Levulan® PDT therapy until June, 2019.
 Conference Call Details and Dial-in Information:
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3-months ended March 31,2010
    
    
    2009(Unaudited)
    
    
    (Unaudited)PDT Drug & Device Product RevenuesKerastick® Product Revenues:United States
    
    $
    7,549,000
    
    
    $
    5,685,000Canada
    
    
    57,000
    
    
    
    135,000Korea
    
    
    109,000
    
    
    
    170,000Rest of World
    
    
    87,000
    
    
    
    87,000Subtotal Kerastick® Product Revenues
    
    
    7,802,000
    
    
    
    6,077,000BLU-U® Product Revenues:United States
    
    
    489,000
    
    
    
    642,000Canada
    
    
    5,000
    
    
    
    Subtotal BLU-U® Product Revenues
    
    
    494,000
    
    
    
    642,000Total PDT Drug & Device Product Revenues
    
    
    8,296,000
    
    
    
    6,719,000Total Non-PDT Drug Product Revenues
    
    
    418,000
    
    
    
    419,000TOTAL PRODUCT REVENUES
    
    $
    8,714,000
    
    
    $
    7,138,000




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March 31,2009
    
    
    December 31,(Unaudited)
    
    
    2009ASSETSCURRENT ASSETSCash and cash equivalents
    
    $
    8,541,965
    
    
    $
    7,613,378Marketable securities
    
    
    9,019,112
    
    
    
    9,055,959Accounts receivable, net
    
    
    2,059,100
    
    
    
    2,629,189Inventory
    
    
    1,946,592
    
    
    
    2,170,275Prepaid and other current assets
    
    
    1,191,080
    
    
    
    1,561,467TOTAL CURRENT ASSETS
    
    
    22,757,849
    
    
    
    23,030,268Restricted cash
    
    
    174,346
    
    
    
    174,255Property, plant and equipment, net
    
    
    1,586,323
    
    
    
    1,660,755Deferred charges and other assets
    
    
    68,099
    
    
    
    68,099TOTAL ASSETS
    
    $
    24,586,617
    
    
    $
    24,933,377LIABILITIES AND SHAREHOLDERS EQUITYCURRENT LIABILITIESAccounts payable
    
    $
    965,347
    
    
    $
    630,144Accrued compensation
    
    
    736,704
    
    
    
    1,260,609Other accrued expenses
    
    
    2,549,852
    
    
    
    2,456,612Deferred revenue
    
    
    739,023
    
    
    
    902,597TOTAL CURRENT LIABILITIES
    
    
    4,990,926
    
    
    
    5,249,962Deferred revenues
    
    
    2,910,562
    
    
    
    2,906,020Warrant liability
    
    
    1,012,180
    
    
    
    812,905Other liabilities
    
    
    108,684
    
    
    
    123,016TOTAL LIABILITIES
    
    
    9,022,352
    
    
    
    9,091,903SHAREHOLDERS EQUITYCapital stockAuthorized: 100,000,000 shares;
40,000,000 shares designated as common
stock, no par, and 60,000,000 shares
issuable in series or classes; and 40,000
junior Series A preferred shares. Issued
and outstanding: 24,173,096 and
24,108,908 shares of common stock, no
par, at March 31, 2010 and December 31,
2009, respectively
    
    
    151,747,588
    
    
    
    151,683,399Additional paid-in capital
    
    
    8,409,025
    
    
    
    8,291,805Accumulated deficit
    
    
    (144,783,700
    )
    
    
    (144,359,217
    )Accumulated other comprehensive loss
    
    
    191,352
    
    
    
    225,487TOTAL SHAREHOLDERS EQUITY
    
    
    15,564,265
    
    
    
    15,841,474TOTAL LIABILITIES AND SHAREHOLDERS EQUITY
    
    $
    24,586,617
    
    
    $
    24,933,377




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3-months ended March 31,2010
    
    
    2009(Unaudited)
    
    
    (Unaudited)Product revenues
    
    $
    8,713,880
    
    
    $
    7,138,269Cost of product revenues and royalties
    
    
    1,818,185
    
    
    
    1,938,226Gross margin
    
    
    6,895,695
    
    
    
    5,200,043Operating costs:Research and development
    
    
    1,109,667
    
    
    
    1,185,095Marketing and sales
    
    
    3,613,799
    
    
    
    3,410,104General and administrative
    
    
    2,463,164
    
    
    
    2,141,450Total operating costs
    
    
    7,186,630
    
    
    
    6,736,649Income/(loss) from operations
    
    
    (290,935
    )
    
    
    (1,536,606
    )Other income:Income/(loss) on change in fair value of warrants
    
    
    (199,275
    )
    
    
    (134,912
    )Other Income, net
    
    
    65,727
    
    
    
    64,587Net income/(loss)
    
    $
    (424,483
    )
    
    $
    (1,606,931
    )Basic and diluted net loss per common share
    
    $
    (0.02
    )
    
    $
    (0.07
    )Weighted average number of common shares
    
    
    24,122,459
    
    
    
    24,089,452




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Use of Non-GAAP Financial Measures
   3-months ended March 31,2010
    
    
    2009(Unaudited)
    
    
    (Unaudited)GAAP net income/(loss)
    
    $
    (424,483
    )
    
    $
    (1,606,931
    )Share-based compensation (a)
    
    
    211,778
    
    
    
    199,127Consideration to former Sirius shareholders (b)
    
    
    4,500
    
    
    
    Change in fair value of warrants (c)
    
    
    199,275
    
    
    
    134,912Non-GAAP adjusted net income/(loss)
    
    $
    (8,930
    )
    
    $
    (1,272,892
    )Non-GAAP basic and diluted net income/(loss) per common share
    
    $
    (0.00
    )
    
    $
    (0.05
    )Weighted average number of common shares
    
    
    24,122,459
    
    
    
    24,089,452
 
 (a)
    
    Share-based compensation expense resulting from the application of SFAS 123(R).(b)
    
    Milestone payment related to Sirius Laboratories acquisition.(c)
    
    Non-cash gain/loss on change in fair value of warrants.




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