<PAGE>
--------------------------------------------------------------------------------
--------------------------------------------------------------------------------

                       SECURITIES AND EXCHANGE COMMISSION

                             WASHINGTON, D.C. 20549

                            ------------------------

                                   FORM 10-Q

(MARK ONE)

<TABLE>
<S>        <C>
   /X/       QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE
                         SECURITIES EXCHANGE ACT OF 1934
</TABLE>

               For the quarterly period ended: SEPTEMBER 30, 1999
                                       OR

<TABLE>
<S>        <C>
   / /       TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE
                         SECURITIES EXCHANGE ACT OF 1934
</TABLE>

        For the transition period from ______________ to ______________

                         COMMISSION FILE NUMBER 0-19410

                            ------------------------

                                 SEPRACOR INC.
                         -----------------------------

             (Exact Name of Registrant as Specified in its Charter)

<TABLE>
<S>                                            <C>
               DELAWARE                                     22-2536587
      --------------------------                    --------------------------
    (State or Other Jurisdiction of              (I.R.S. Employer Identification
    Organization or Incorporation)                           number)
</TABLE>

               111 LOCKE DRIVE, MARLBOROUGH, MASSACHUSETTS 01752
          -----------------------------------------------------------
              (Address of Principal Executive Offices) (Zip Code)

                                 (508) 481-6700
                                  ------------
              (Registrant's Telephone Number, Including Area Code)

                            ------------------------

    Indicate by check mark whether the registrant (1) has filed all reports
required to be filed by Section 13 or 15(d) of the Securities Exchange Act of
1934 during the preceding 12 months (or for such shorter period that the
registrant was required to file such reports), and (2) has been subject to such
filing requirements for the past 90 days.

                                Yes /X/  No / /

    Indicate the number of shares outstanding of each of the issuer's classes of
common stock, as of the latest practicable date.

    COMMON STOCK, PAR VALUE $.10 PER SHARE, 33,135,047 SHARES OUTSTANDING AT
NOVEMBER 5, 1999.

--------------------------------------------------------------------------------
--------------------------------------------------------------------------------
<PAGE>
                                 SEPRACOR INC.
                                     INDEX

<TABLE>
<S>                                                                                         <C>
Part I--Financial Information
Item 1. Consolidated Condensed Financial Statements
  Consolidated Condensed Balance Sheets as of September 30, 1999 and December 31, 1998
    (Unaudited)...........................................................................      3
  Consolidated Statements of Operations for the Three and Nine Month Periods Ended
    September 30, 1999 and 1998 (Unaudited)...............................................      4
  Consolidated Statements of Cash Flows for the Nine Month Periods Ended
    September 30, 1999 and 1998 (Unaudited)...............................................      5
  Notes to Consolidated Interim Financial Statements......................................      6
Item 2. Management's Discussion and Analysis of Financial Condition
  and Results of Operations...............................................................     12
Item 3. Quantitative and Qualitative Disclosure About Market Risk.........................     23

Part II--Other Information
Item 1. Legal Proceedings.................................................................     24
Item 6. Exhibits and Reports on Form 8-K..................................................     25
Signatures................................................................................     26
</TABLE>

                                       2
<PAGE>
                                 SEPRACOR INC.

                     CONSOLIDATED CONDENSED BALANCE SHEETS

                                  (UNAUDITED)
                                 (IN THOUSANDS)

<TABLE>
<CAPTION>
                                                              SEPTEMBER 30,   DECEMBER 31,
                                                                  1999            1998
                                                              -------------   ------------
<S>                                                           <C>             <C>
ASSETS

Current Assets:
  Cash and cash equivalents.................................    $ 30,560        $295,323
  Marketable securities.....................................     347,238         204,274
  Accounts receivable, net..................................       2,827              --
  Inventories, net..........................................       6,208              --
  Other current assets......................................       5,074           3,386
                                                                --------        --------
  Total Current Assets......................................     391,907         502,983

Property, plant and equipment, net..........................      18,963          16,508
Deferred financing costs, net...............................      13,286          15,119
Patents and intangible assets, net..........................      21,156           2,677
Investment in affiliates....................................       2,058           1,490
Net assets from discontinued operations.....................          --          10,325
Other assets................................................       1,228             158
                                                                --------        --------
  Total Assets..............................................    $448,598        $549,260
                                                                ========        ========
LIABILITIES AND STOCKHOLDERS' EQUITY (DEFICIT)

Current Liabilities:
  Accounts payable..........................................    $  7,564        $  9,290
  Accrued expenses..........................................      44,113          31,275
  Notes payable and current portion of capital lease
    obligation and long-term debt...........................         446           2,410
  Deferred revenue and other current liabilities............       2,658           2,502
                                                                --------        --------
  Total Current Liabilities.................................      54,781          45,477

Loan guarantee of affiliate.................................       5,000           5,000
Long-term debt and capital lease obligation.................       2,176           2,435
Convertible subordinated debentures.........................     489,475         489,475
                                                                --------        --------
  Total Liabilities.........................................     551,432         542,387

Minority interest...........................................       1,462           2,445

Stockholders' Equity (Deficit)
  Preferred stock...........................................          --              --
  Common stock..............................................       3,311           3,266
  Additional paid-in capital................................     321,954         307,668
  Unearned compensation, net................................        (119)           (144)
  Accumulated deficit.......................................    (428,986)       (306,311)
  Accumulated other comprehensive income (loss).............        (456)            (51)
                                                                --------        --------
Total Stockholders' Equity (Deficit)........................    (104,296)          4,428
                                                                --------        --------
  Total Liabilities and Stockholders' Equity (Deficit)......    $448,598        $549,260
                                                                ========        ========
</TABLE>

                  The accompanying notes are an integral part
                    of the consolidated financial statements

                                       3
<PAGE>
                                 SEPRACOR INC.
                     CONSOLIDATED STATEMENTS OF OPERATIONS
                                  (UNAUDITED)
                    (IN THOUSANDS, EXCEPT PER SHARE AMOUNTS)

<TABLE>
<CAPTION>
                                              THREE MONTH PERIODS ENDED       NINE MONTH PERIODS ENDED
                                            -----------------------------   -----------------------------
                                            SEPTEMBER 30,   SEPTEMBER 30,   SEPTEMBER 30,   SEPTEMBER 30,
                                                1999            1998            1999            1998
                                            -------------   -------------   -------------   -------------
<S>                                         <C>             <C>             <C>             <C>
Revenues:
  Product.................................     $  2,392        $     34       $   7,619        $    124
  Collaborative research and
    development...........................           --           1,368           2,390           3,618
  License fees............................           --               8              11           5,038
  Royalties...............................           91              61             201             175
                                               --------        --------       ---------        --------
    Total Revenues........................        2,483           1,471          10,221           8,955
Cost of revenues:
  Product.................................          877              20           2,157              75
  License fees............................           --              --              --             400
  Royalties...............................           29              21              70              57
                                               --------        --------       ---------        --------
    Total Cost of Revenues................          906              41           2,227             532
    Gross Margin..........................        1,577           1,430           7,994           8,423
Operating Expenses:
  Research and development................       34,690          20,151          77,252          43,490
  Sales and marketing.....................       15,560           6,460          30,935          11,820
  General and administrative..............        3,512           2,115          10,257           5,918
  Patent costs............................        1,024             476           2,554           1,412
                                               --------        --------       ---------        --------
    Total Operating Expenses..............       54,786          29,202         120,998          62,640
                                               --------        --------       ---------        --------
Loss from operations......................      (53,209)        (27,772)       (113,004)        (54,217)
Other income (expense):
  Interest income.........................        5,304           3,483          16,975           9,459
  Interest expense........................       (8,276)         (4,502)        (24,834)        (12,132)
  Other income (expense)..................           70              87             132             (43)
  Equity in loss of investees.............           --            (600)         (2,509)         (1,846)
                                               --------        --------       ---------        --------
    Total Other Income (Expense)..........       (2,902)         (1,532)        (10,236)         (4,562)
                                               --------        --------       ---------        --------
Net loss before minority interests........      (56,111)        (29,304)       (123,240)        (58,779)
Minority interest in subsidiary...........          362             134             910             291
                                               --------        --------       ---------        --------
Net loss from continuing operations.......     $(55,749)       $(29,170)      $(122,330)       $(58,488)
                                               --------        --------       ---------        --------
Discontinued Operations:
  Loss from discontinued operations (net
    of minority interests)................           --            (458)           (345)           (442)
                                               --------        --------       ---------        --------
Net loss..................................     $(55,749)       $(29,628)      $(122,675)       $(58,930)
                                               --------        --------       ---------        --------
Basic and diluted net loss per common
  share from continuing operations........     $  (1.68)       $  (1.03)      $   (3.72)       $  (2.08)
                                               --------        --------       ---------        --------
Basic and diluted net loss per common
  share from discontinued operations......     $     --        $  (0.02)      $   (0.01)       $  (0.02)
                                               --------        --------       ---------        --------
Basic and diluted net loss per common
  share...................................     $  (1.68)       $  (1.05)      $   (3.73)       $  (2.10)
                                               --------        --------       ---------        --------
Shares used in computing basic and diluted
  net loss per common share:
  Basic and diluted.......................       33,098          28,315          32,873          28,092
                                               --------        --------       ---------        --------
</TABLE>

                  The accompanying notes are an integral part
                    of the consolidated financial statements

                                       4
<PAGE>
                                 SEPRACOR INC.
                     CONSOLIDATED STATEMENTS OF CASH FLOWS
                                  (UNAUDITED)
                                 (IN THOUSANDS)

<TABLE>
<CAPTION>
                                                                NINE MONTH PERIODS ENDED
                                                              -----------------------------
                                                              SEPTEMBER 30,   SEPTEMBER 30,
                                                                  1999            1998
                                                              -------------   -------------
<S>                                                           <C>             <C>
Cash flows from operating activities:
Net loss....................................................    $(122,675)      $ (58,930)
Less: Net loss from discontinued operations
  (net of minority interests)...............................         (345)           (442)
                                                                ---------       ---------
    Net loss from continuing operations.....................     (122,330)        (58,488)
Adjustments to reconcile net loss to net cash used in
  operating activities:
  Minority interests in subsidiaries........................         (910)           (291)
  Depreciation and amortization.............................        5,134           2,827
  Provision for discounts and allowances....................           82              --
  Equity in investee losses.................................        2,509           1,846
  Loss on disposal of property and equipment................            6              14
Changes in operating assets and liabilities:
  Accounts receivable.......................................       (2,143)         (2,224)
  Inventories...............................................       (5,814)             --
  Other current assets and liabilities......................       (2,553)            717
  Accounts payable..........................................       (2,097)            819
  Accrued expenses..........................................       12,499          12,768
                                                                ---------       ---------
    Net cash used in operating activities:..................     (115,617)        (42,012)
Cash flows used in investing activities:
  Purchases of marketable securities........................     (832,481)       (210,916)
  Sales of marketable securities............................      689,517         111,510
  Additions to property and equipment.......................       (5,567)         (4,533)
  Purchase of intangible assets.............................      (10,000)             --
  Investment in affiliate...................................       (2,000)             75
  Promissory note to affiliate..............................         (500)             --
  Decrease in other assets..................................          148             567
                                                                ---------       ---------
    Net cash used in investing activities:..................     (160,883)       (103,297)
Cash flows from financing activities:
  Net proceeds from issuance of common stock................        5,304           4,760
  Issuance of warrants......................................           --              31
  Repurchase of redeemable preferred stock..................           --          (6,850)
  Proceeds from sale of 6 1/4% debentures due 2005..........           --         189,475
  Costs associated with 6 1/4% debentures due 2005..........           --          (6,105)
  Costs associated with 7% debentures due 2005..............         (276)             --
  Net repayments of long-term debt and capital leases.......         (794)         (1,006)
  Net borrowings (repayments) under line of credit
    agreements..............................................       (2,032)          1,917
                                                                ---------       ---------
    Net cash provided by financing activities...............        2,202         182,222
Effect of exchange rates on cash and cash equivalents.......         (405)           (308)
                                                                ---------       ---------
Net increase (decrease) in cash and cash equivalents........     (274,703)         36,605
Net cash provided by discontinued operations................        9,940             182
Cash and cash equivalents at beginning of period............      295,323          82,579
                                                                ---------       ---------
Cash and cash equivalents at end of period..................    $  30,560       $ 119,366
Non cash activities:
Common stock issued for intangible asset....................    $  (7,950)      $      --
Acquisition of BioSphere Medical:
  Liabilities assumed.......................................    $  (1,493)      $      --
  Fair value of assets acquired.............................        1,493       $      --
</TABLE>

                  The accompanying notes are an integral part
                    of the consolidated financial statements

                                       5
<PAGE>
                                    ITEM 1.

               NOTES TO CONSOLIDATED INTERIM FINANCIAL STATEMENTS

1.  Basis of presentation:

    The accompanying consolidated interim financial statements are unaudited and
have been prepared on a basis substantially consistent with the audited
financial statements. Certain information and footnote disclosures normally
included in Sepracor's annual financial statements have been condensed or
omitted. The year-end consolidated condensed balance sheet data was derived from
audited financial statements but does not include all disclosures required by
generally accepted accounting principles. The consolidated interim financial
statements, in the opinion of management, reflect all adjustments (including
normal recurring accruals) necessary for a fair presentation of the results for
the interim periods ended September 30, 1999 and 1998.

    The results of operations for the interim periods are not necessarily
indicative of the results of operations to be expected for the fiscal year.
These consolidated interim financial statements should be read in conjunction
with the audited financial statements for the year ended December 31, 1998,
which are contained in Sepracor's Annual Report on Form 10-K for the year ended
December 31, 1998, filed with the Securities and Exchange Commission.

    The consolidated interim financial statements include the accounts of
Sepracor Inc. ("Sepracor") and its majority and wholly owned subsidiaries,
including BioSphere Medical Inc. ("BioSphere") formerly BioSepra Inc., and
Sepracor Canada Limited.

2.  Discontinued operations:

    On May 17, 1999, BioSphere completed the sale of substantially all its
assets related to its biopharmaceutical drug purification and research
consumable business to Life Technologies for net cash proceeds of approximately
$11,158,000.

    Sepracor's results of operations and the related footnote information for
the three and nine months ended September 30, 1999 and 1998 exclude the results
of the BioSphere biopharmaceutical drug purification and research consumable
business from continuing operations, revenues and other components of income and
expense. The discontinued operations results are presented separately in a
single caption entitled "Loss from discontinued operations, net of minority
interests." The loss for the nine-month period ended September 30, 1999 includes
a $69,000 loss on the sale of the discontinued assets. Revenues from the
discontinued operations were $0 and $2,521,000 for the three and nine months
ended September 30, 1999, respectively, and $1,220,000 and $4,853,000 for the
three and nine months ended September 30, 1998, respectively. The loss from
discontinued operations, net of minority interests, was $0 and $345,000 for the
three and nine months ended September 30, 1999, respectively, and was $458,000
and $442,000 for the three and nine months ended September 30, 1998,
respectively.

    The consolidated statements of cash flows for the nine months ended
September 30, 1999 includes discontinued operations and 1998 has been restated
to reflect the discontinued operation. The cash flows from discontinued
operations have been summarized into a single line entitled "net cash provided
from discontinued operations."

                                       6
<PAGE>
                                    ITEM 1.

         NOTES TO CONSOLIDATED INTERIM FINANCIAL STATEMENTS (CONTINUED)

3.  Inventories, patents and intangible assets, net:

    Inventories consist of the following:

<TABLE>
<CAPTION>
(IN THOUSANDS)                                                SEPTEMBER 30, 1999   DECEMBER 31, 1998
--------------                                                ------------------   -----------------
<S>                                                           <C>                  <C>
Raw materials...............................................        $2,312             $      --
Work in progress............................................           923                    --
Finished goods..............................................         2,973                    --
                                                                    ------             ---------
                                                                    $6,208             $      --
</TABLE>

    At September 30, 1999, the inventory balances related primarily to Xopenex
inventory. At December 31, 1998, the net assets of BioSphere's discontinued
operations included inventory of $3,572,000.

    Patents and intangible assets, net of amortization, were $21,156,000 and
$2,677,000 at September 30, 1999 and December 31, 1998, respectively.

    In August 1999, Sepracor paid Georgetown University $10,000,000 in cash and
issued 100,000 shares of Sepracor common stock to obtain all rights, title and
interest held by Georgetown relating to terfenadine carboxylate, norastemizole,
intraconazole enantiomers, and ketoconazole enantiomers. The intellectual
property rights purchased from Georgetown are being amortized over a ten year
period.

4.  Basic and diluted net loss per common share:

    Basic net loss per common share ("EPS") excludes dilution and is computed by
dividing income available to common shareholders by the weighted average number
of common shares outstanding for the period. Diluted EPS is based upon the
weighted average number of common shares outstanding during the period plus the
additional weighted average common equivalent shares during the period. Common
equivalent shares are not included in the per share calculations where the
effect of their inclusion would be anti-dilutive. Common equivalent shares
result from the assumed conversion of preferred stock and convertible debt and
the assumed exercises of outstanding stock options, the proceeds of which are
then assumed to have been used to repurchase outstanding common stock using the
treasury stock method. For the three and nine months ended September 30, 1999
and 1998, basic and diluted net loss per common share is computed based on the
weighted-average number of common shares outstanding during the period, because
the effect of common stock equivalents would be anti-dilutive.

    Included in the three and nine months ended September 30, 1999 and 1998 net
loss applicable to common shares is $0, and $0, and $0 and $150, respectively,
of dividends relating to series B redeemable exchangeable preferred stock (see
table below). Certain securities were not included in the computation of diluted
earnings per share for the three and nine months ended September 30, 1999 and
1998, because they would have an anti-dilutive effect due to net losses for such
periods. These securities include: (i) options to purchase 5,325,605 shares of
common stock with purchase prices of $2.00 to $118.25 per share for the three
and nine months ended September 30, 1999 and options to purchase 4,535,312
shares of common stock with purchase prices of $1.00 to $48.63 per share for the
three and nine months ended September 30, 1998; and (ii) 6,402,381 shares of
common stock for issuance upon conversion of the 7% convertible subordinated
debentures due 2005 and the 6 1/4% convertible subordinated debentures due 2005
for the three and nine months ended September 30, 1999 and 8,101,302 shares of
common stock for

                                       7
<PAGE>
                                    ITEM 1.

         NOTES TO CONSOLIDATED INTERIM FINANCIAL STATEMENTS (CONTINUED)

issuance upon conversion of the 7% convertible subordinated debentures due 2002
and the 6 1/4% convertible subordinated debentures due 2005 for the three and
nine months ended September 30, 1998.

<TABLE>
<CAPTION>
                                              THREE MONTH PERIODS ENDED       NINE MONTH PERIODS ENDED
                                            -----------------------------   -----------------------------
                                            SEPTEMBER 30,   SEPTEMBER 30,   SEPTEMBER 30,   SEPTEMBER 30,
(IN THOUSANDS)                                  1999            1998            1999            1998
--------------                              -------------   -------------   -------------   -------------
<S>                                         <C>             <C>             <C>             <C>
Net loss applicable to common shares:
Net loss..................................     $(55,749)       $(29,628)      $(122,675)       $(58,930)
Dividends on preferred stock..............           --              --              --            (150)
                                               --------        --------       ---------        --------
Net loss applicable to common shares:.....     $(55,749)       $(29,628)      $(122,675)       $(59,080)
</TABLE>

5.  Comprehensive income (loss):

    Total comprehensive income (loss) is comprised of net income (loss) and net
currency translation adjustments.

<TABLE>
<CAPTION>
                                              THREE MONTH PERIODS ENDED       NINE MONTH PERIODS ENDED
                                            -----------------------------   -----------------------------
                                            SEPTEMBER 30,   SEPTEMBER 30,   SEPTEMBER 30,   SEPTEMBER 30,
(IN THOUSANDS)                                  1999            1998            1999            1998
--------------                              -------------   -------------   -------------   -------------
<S>                                         <C>             <C>             <C>             <C>
Comprehensive income (loss):
Net loss..................................     $(55,749)       $(29,628)      $(122,675)       $(58,930)
Cumulative translation adjustment.........         (218)            (98)           (405)           (238)
                                               --------        --------       ---------        --------
Total comprehensive income (loss).........     $(55,967)       $(29,726)      $(123,080)       $(59,168)
</TABLE>

6.  Business segments:

    Sepracor is a research based pharmaceutical company engaged in the
discovery, development and marketing of pharmaceutical products. Previously, the
Company presented information with BioSphere as a separate segment and included
an "other" column for equity in investee losses and minority interests. Based on
BioSphere discontinuing a material portion of its operations, Sepracor
management has reviewed information as one business segment since June 1999.

7.  Summarized financial information regarding affiliates:

    HemaSure

    On February 25, 1999, Sepracor entered into an agreement with HemaSure
pursuant to which Sepracor invested $2,000,000 in HemaSure in exchange for
1,333,334 shares of HemaSure common stock and for warrants to purchase 667,000
additional shares of HemaSure common stock.

    On May 4, 1999, HemaSure completed a private placement financing with COBE
Laboratories, Inc. ("COBE LABS"), which is wholly-owned by Gambro AB. COBE LABS
purchased 4.5 million shares of HemaSure common stock for an aggregate purchase
price of $9.0 million. As a result of this investment, COBE LABS acquired
approximately 30% of HemaSure's outstanding common stock and Sepracor's
ownership of HemaSure was reduced to approximately 29%. The agreement also
provides COBE LABS with an option to purchase an additional $3 million of
HemaSure common stock at any time between August 3, 1999 and May 3, 2000. Should
COBE LABS exercise its option, the number of shares to be issued will be based
upon the average closing price of HemaSure's common stock for the 30-day period
prior to the exercise.

    For the nine month period ended September 30, 1999, Sepracor recognized
$2,000,000 as its ownership share of HemaSure losses. Sepracor's investment in
HemaSure is zero at September 30, 1999.

                                       8
<PAGE>
                                    ITEM 1.

         NOTES TO CONSOLIDATED INTERIM FINANCIAL STATEMENTS (CONTINUED)

    Versicor

    On March 31, 1999, Versicor sold 500,000 shares of preferred stock to
Novartis Pharma AG, as part of a joint collaboration to discover certain new
antibacterials.

    On April 2, 1999, Versicor sold 500,000 shares of preferred stock to
Pharmacia & Upjohn, as part of a joint collaboration to discover certain new
antibacterials.

    As a result of the Novartis and Pharmacia & Upjohn equity investments in
Versicor, Sepracor recorded a gain of $1,077,000 which was recorded through
additional paid-in-capital and Sepracor's ownership percentage of Versicor was
reduced to approximately 18%. Effective April 1999, Sepracor has changed its
accounting for its investment in Versicor to the cost method of accounting from
the equity method. Sepracor recorded $508,741 as its share of Versicor losses
through April, 1999. At September 30, 1999, Sepracor's investment in Versicor
was approximately $2,058,000.

    On June 29, 1999, Sepracor loaned Versicor $500,000 under a promissory note
agreement.

    The following is the summarized income statement information for the
Company's subsidiaries HemaSure and Versicor for the three and nine month
periods ended September 30, 1999 and 1998:

<TABLE>
<CAPTION>
                                              THREE MONTH PERIODS ENDED       NINE MONTH PERIODS ENDED
                                            -----------------------------   -----------------------------
                                            SEPTEMBER 30,   SEPTEMBER 30,   SEPTEMBER 30,   SEPTEMBER 30,
(IN THOUSANDS)                                  1999            1998            1999            1998
--------------                              -------------   -------------   -------------   -------------
<S>                                         <C>             <C>             <C>             <C>
HemaSure:
Net sales.................................     $   119         $    --         $    132        $    25
Gross profit (loss).......................        (530)             --           (1,300)          (632)
Loss from operations......................      (2,236)         (2,667)          (6,953)        (9,029)
Net loss..................................     $(2,543)        $(2,682)        $ (7,934)       $(8,974)

Versicor:
Net sales.................................     $ 1,550         $    --         $  3,200        $    --
Gross profit (loss).......................       1,550              --            3,200             --
Loss from operations......................      (1,286)         (2,429)         (15,138)        (8,614)
Net loss..................................     $(1,467)        $(2,386)        $(15,340)       $(8,392)
</TABLE>

8.  Litigation:

    On February 12, 1999, the Federal Trade Commission ("FTC") issued a request
for additional information or documentary materials relating to the Company's
exclusive license agreement with Eli Lilly and Company (the "Lilly Agreement").
The purpose of the request was to investigate whether or not the Lilly Agreement
constitutes a violation of Section 5 of the Federal Trade Commission Act and
Section 7 of the Clayton Act. The Company is in the process of responding to the
request. At the conclusion of its investigation, the FTC could institute
proceedings seeking to modify the Lilly Agreement or to prevent it from becoming
effective. While the Company believes that the Lilly Agreement does not
constitute a violation of the above-mentioned laws, the Company is unable to
predict the outcome of the proceeding.

    The interference declared on June 30, 1999 between Sepracor and
Rhone-Poulenc Rorer S.A. ("RPR") relating to (+)-zopiclone will be dissolved by
Sepracor's agreement with RPR of October 7, 1999, under which RPR's involved
patent application will be assigned to Sepracor. (See Note 9, Subsequent events)

    All legal proceedings between Sepracor and Hoechst Marion Roussel ("HMR")
relating to fexofenadine, including foreign litigation and the interference
between Sepracor and HMR, have been settled

                                       9
<PAGE>
                                    ITEM 1.

         NOTES TO CONSOLIDATED INTERIM FINANCIAL STATEMENTS (CONTINUED)

by Sepracor's agreement with HMR of September 1, 1999. (See Item 2, Management's
Discussion and Analysis of Financial Condition and Results of Operations)

    HemaSure is a defendant in two lawsuits brought by Pall Corporation
("Pall"). In complaints filed in February 1996 and November 1996, Pall alleged
that HemaSure's manufacture, use and/or sale of the LeukoNet product infringes
upon three patents held by Pall. On October 14, 1996, in connection with the
first action concerning U.S. Patent No. 5,451,321 (the "321 Patent"), HemaSure
filed a motion for summary judgment of noninfringement. Pall filed a cross
motion for summary judgment of infringement at the same time. In October 1997,
the U.S. District Court of the Eastern District of New York ("EDNY") granted in
part Pall's summary judgment motion and held that the LeukoNet product infringes
a single claim from the "321 Patent. HemaSure has terminated the manufacture,
use, sale and offer for sale of the filter subject to the court's order.
HemaSure appealed the October 1997 decision to the Court of Appeals for the
Federal Circuit. In June 1999, the Court of Appeals for the Federal Circuit
determined that the LeukoNet product did not infringe the claim of the "321
patent.

    With respect to the second action concerning U.S. Patent No's. 4,952,572
(the "572 Patent") and 4,340,479 (the "479 patent"), HemaSure has answered the
complaint stating that it does not infringe any claim of the asserted patents.
Further, HemaSure has counterclaimed for declaratory judgment of invalidity,
noninfringement and unenforceability of the "572 Patent. Pall has amended its
complaint to add Lydall, Inc. ("Lydall"), whose subsidiary supplied filter media
for the LeukoNet product, as a co-defendant and has dropped its claim that the
LeukoNet product infringes the "479 patent. HemaSure has filed for summary
judgment of noninfringement, and Pall has cross-filed for summary judgment of
infringement at the same time. Lydall supported HemaSure's motion for summary
judgment of noninfringement, and has served a motion for summary judgment that
the asserted claims of the "572 Patent are invalid as a matter of law. Discovery
has been completed in the action.

    On April 5, 1999, HemaSure and COBE BCT, Inc. ("COBE BCT") filed a complaint
for declaratory relief against Pall in the U.S. District Court of Colorado.
HemaSure and COBE BCT seek declaratory relief that Pall's U.S. Patent No's.
4,925,572, 5,229,012, 5,344,561, 5,451,321, 5,501,795 and 5,863,436 are invalid
and not infringed by HemaSure's r\LS filter and methods of using the r\LS
filter. Pall moved to dismiss, to transfer, or, in the alternative, to stay this
action and HemaSure and COBE BCT opposed Pall's motion. On July 16, 1999, the
U.S. District Court of Colorado denied Pall's motion to transfer and on
September 30, 1999 the court denied Pall's motion to dismiss. Discovery is now
proceeding.

    On April 23, 1999, Pall filed a complaint against HemaSure and COBE BCT in
the EDNY alleging that HemaSure's r\LS filter infringes Pall's "572 patent,
tortuously interfered and unfairly competed with Pall's business. HemaSure was
served with the complaint on April 30, 1999. On May 19, 1999, Pall filed an
amended complaint in the EDNY adding Sepracor, COBE Laboratories, Inc. ("COBE
LABS"), Gambro, A.B. as defendants and alleging that Sepracor induced and
contributed to HemaSure's alleged infringement of Pall's "572 patent, and
allegedly tortuously interfered and unfairly competed with Pall's business.
Sepracor was served with the amended complaint on June 1, 1999. Sepracor,
HemaSure and COBE LABS have moved to dismiss, transfer, or stay the action, and
Pall has opposed the motion.

    HemaSure believes, based on advice of its legal counsel, that a properly
informed court should conclude that the manufacture, use and/or sale by HemaSure
or its customers of the LeukoNet product and the r\LS product did not infringe
any valid enforceable claim of the Pall patents. However, there can be no
assurance that HemaSure will prevail in the pending litigation, and an adverse
outcome in a patent infringement action would have a material adverse effect on
HemaSure's financial condition and future business and operations.

                                       10
<PAGE>
                                    ITEM 1.

         NOTES TO CONSOLIDATED INTERIM FINANCIAL STATEMENTS (CONTINUED)

    Sepracor believes, based on advice of its legal counsel, that a properly
informed court should conclude that Pall's suit against Sepracor should be
dismissed. However, there can be no assurance that this suit will be dismissed
or that Sepracor will prevail in the pending litigation.

9.  Subsequent events:

    On October 7, 1999, Sepracor announced that it had entered into an agreement
with Rhone-Poulenc Rorer SA, whereby Sepracor has exclusively licensed RPR's
pre-clinical, clinical and post-marketing surveillance data package relating to
zopiclone, its isomers and metabolites, to develop, make, use and sell
(+)-zopiclone in the United States. RPR will assign all U.S. patent applications
relating to (+)-zopiclone to Sepracor. Pursuant to the agreement, RPR retains
the right under the licensed data package to manufacture (+)-zopiclone in the
U.S. for non-U.S. markets. In addition, Sepracor has paid a license fee to RPR
and will pay a royalty to RPR on (+)-zopiclone product sales, if any, in the
United States. Sepracor may also be required to pay RPR milestone payments.

    On October 5, 1999, COBE Laboratories, Inc. exercised its option to purchase
$3 million of HemaSure common stock as part of its May 1999 private placement
agreement with HemaSure. As a result of the transaction, Sepracor's ownership of
HemaSure was reduced to approximately 27%.

    On October 29, 1999, Versicor completed a private placement financing
arrangement of approximately $40 million. As a result of the transaction,
Sepracor paid an additional $500,000 to Versicor under a promissory note
agreement and Sepracor's $1,000,000 note receivable was then converted into
Versicor preferred stock. Sepracor's ownership of Versicor was reduced to
approximately 11%.

                                       11
<PAGE>
ITEM 2.  MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS
         OF OPERATIONS

    This Quarterly Report on Form 10-Q contains, in addition to historical
information, forward-looking statements, which involve risk and uncertainties.
Sepracor's actual results could differ significantly from the results discussed
in such forward-looking statements. See "Factors Affecting Future Operating
Results" below.

OVERVIEW

    The consolidated interim financial statements include the accounts of
Sepracor Inc. ("Sepracor") and its majority and wholly owned subsidiaries,
including BioSphere Medical Inc. ("BioSphere"), which was formerly known as
BioSepra Inc.("BioSepra") and Sepracor Canada Limited.

    On February 25, 1999, Sepracor entered into an agreement with HemaSure
pursuant to which Sepracor invested $2,000,000 in HemaSure in exchange for
1,333,334 shares of HemaSure common stock and for warrants to purchase 667,000
of additional shares of HemaSure common stock.

    On February 25, 1999, BioSphere acquired 51% of the outstanding common stock
of BioSphere Medical, S.A. ("BioSphere SA"). BioSphere acquired the 51%
ownership by granting an exclusive license pertaining to certain patents and
technology and the transfer of certain other technology to BioSphere SA.
BioSphere has the option to acquire the remaining 49% of the outstanding common
stock of BioSphere SA, through December 31, 2004. The results of operations for
BioSphere SA are included in BioSphere's operations from the date of
acquisition. The historical results of operations of BioSphere SA are not
material to BioSphere's financial statements.

    On March 26, 1999, Sepracor announced it had received final approval from
the U.S. Food and Drug Administration to market Xopenex(TM) (levalbuterol HCI)
inhalation solution in two dosage strengths for use with a nebulizer for the
treatment and prevention of bronchospasm. In April 1999, commercial sales of
Xopenex commenced.

    On May 14, 1999, Sepracor announced that Johnson & Johnson elected not to
exercise its option to co-promote norastemizole under the agreement, effective
January 1998, between Sepracor and Johnson & Johnson (the "Norastemizole
Agreement"). Sepracor will continue to fund clinical development and marketing
of the drug, which is currently in Phase III clinical trials. Under the terms of
the Norastemizole Agreement, Sepracor has worldwide rights to all Johnson &
Johnson intellectual property covering norastemizole, including the right to
reference data from the astemizole New Drug Application ("NDA"), for
manufacture, development, and marketing of prescription norastemizole products.
In exchange, Johnson & Johnson will receive a royalty on Sepracor's product
sales, if any.

    On May 17, 1999, BioSepra sold substantially all its assets related to its
biopharmaceutical drug purification and research consumable business to Life
Technologies for net cash proceeds of approximately $11,158,000. As a result of
the sale, BioSepra has restated prior year and prior quarter consolidated
financial statement amounts to reflect this business as a discontinued operation
and changed its name to BioSphere Medical Inc.

    On June 1, 1999, Sepracor announced a licensing agreement with UCB Farchim
SA, an affiliate of UCB ("UCB"), relating to levocetirizine, an isomer of ZYRTEC
(racemic cetirizine). Under terms of the agreement, Sepracor has exclusively
licensed to UCB all of Sepracor's issued patents and pending patent applications
regarding levocetirizine in Europe and all other countries, except the United
States and Japan. UCB will begin to pay Sepracor royalties upon first product
sales, if any, and royalties will escalate upon achievement of sales volume
milestones.

    On September 1, 1999, Hoechst Marion Roussel ("HMR") and Sepracor announced
the amendment of an existing business arrangement related to fexofenadine. The
amended arrangement settles all patent

                                       12
<PAGE>
issues between the two companies involving the nonsedating antihistamine
developed and marketed by HMR. Under the terms of a US agreement, Sepracor and
HMR have settled an ongoing arbitrated patent interference involving their US
patent properties, and HMR now owns the Sepracor patent properties. HMR also
obtained an exclusive license to various other Sepracor US patent applications
related to fexofenadine. Sepracor will receive royalties on fexofenadine sales,
if any, in the US upon expiration of HMR's composition of matter patent in
mid-February 2001. Under the terms of a separate ex-US agreement, HMR obtained
an exclusive license to Sepracor's patents that had been subject of litigation
in Europe, as well as various other patent oppositions between the two companies
outside the US. All legal actions outside the US have been settled and Sepracor
is entitled to royalties on fexofenadine product sales effective March 1, 1999
in countries where it has patents in place.

    On October 7, 1999, Sepracor announced that it had entered into an agreement
with Rhone-Poulenc Rorer SA ("RPR"), whereby Sepracor has exclusively licensed
RPR's pre-clinical, clinical and post-marketing surveillance data package
relating to zopiclone, its isomers and metabolites, to develop, make, use and
sell (+)-zopiclone in the United States. RPR will assign all U.S. patent
applications relating to (+)-zopiclone to Sepracor. Pursuant to the agreement,
RPR retains the right under the licensed data package to manufacture
(+)-zopiclone in the U.S. for non-U.S. markets. In addition, Sepracor has paid a
license fee to RPR and will pay a royalty to RPR on (+)-zopiclone product sales,
if any, in the United States. Sepracor may also be required to pay RPR milestone
payments.

THREE AND NINE MONTH PERIODS ENDED SEPTEMBER 30, 1999 AND 1998

    Product revenues were $2,392,000 and $7,619,000 for the three and nine
months ended September 30, 1999, respectively, compared to $34,000 and $124,000,
respectively, for the same periods in 1998. The increase for the three and nine
month periods ended September 30, 1999 is primarily due to sales of Xopenex.

    Collaborative research and development revenues were $0 and $2,390,000 for
the three and nine months ended September 30, 1999, respectively, compared to
$1,368,000 and $3,618,000, respectively, for the same periods in 1998. The
decrease for the three and nine month periods ended September 30, 1999 is
primarily due to the completion of research and development studies relating to
the Norastemizole Agreement in the second quarter of 1999.

    License fees were $0 and $11,000 for the three and nine months ended
September 30, 1999, respectively, compared to $8,000 and $5,038,000,
respectively, for the same periods in 1998. The decrease for the nine-month
period ended September 30, 1999 is primarily due to the $5,000,000 one-time
license payment, which Sepracor received under an agreement with Schering Plough
Corporation entered into in 1998.

    Cost of product revenues, as a percentage of product revenues, were 37% and
28% for the three and nine months ended September 30, 1999, respectively,
compared to 59% and 60%, respectively, for the same periods in 1998. The
decrease for the three and nine month periods ended September 30, 1999 is
primarily due to the introduction of Xopenex product sales in April 1999 which
have significantly less product cost as a percentage of product revenues than
the BioSphere product cost as a percentage of product revenues.

    Research and development expenses were $34,690,000 and $77,252,000 for the
three and nine months ended September 30, 1999, respectively, compared to
$20,151,000 and $43,490,000, respectively, for the same periods in 1998. The
increase for the three and nine month periods ended September 30, 1999 is
primarily due to costs related to several new and anticipated clinical studies
being initiated and increased personnel costs related to the quality assurance,
quality control, clinical and regulatory infrastructure development.

                                       13
<PAGE>
    Sales and marketing expenses were $15,560,000 and $30,935,000 for the three
and nine months ended September 30, 1999, respectively, compared to $6,460,000
and $11,820,000, respectively, for the same periods in 1998. The increase for
the three month period ended September 30, 1999 is primarily due to the addition
of a third-party contracted sales force and the introduction of various
marketing programs for the commercial launch of Xopenex. The increase for the
nine month period ended September 30, 1999 is primarily due to the hiring,
training and salary expense of Sepracor's specialty sales force and the third-
party contracted sales force and the introduction of various marketing programs
for the commercial launch of Xopenex, which commenced in April 1999.

    General and administrative expenses were $3,512,000 and $10,257,000 for the
three and nine months ended September 30, 1999, respectively, compared to
$2,115,000 and $5,918,000, respectively, for the same periods in 1998. The
increase for the three and nine month periods ended September 30, 1999 is
primarily due to higher costs associated with amortization of deferred financing
costs, increased legal costs principally related to the Federal Trade
Commission's review of the Company's agreement, dated December 1998 (the "Lilly
(R)- Fluoxetine Agreement"), with Eli Lilly and Company for R-fluoxetine,
increased personnel costs and increased depreciation expense related to fixed
assets.

    Patent costs were $1,024,000 and $2,554,000 for the three and nine months
ended September 30, 1999, respectively, compared to $476,000 and $1,412,000,
respectively, for the same periods in 1998. The increase for the three and nine
month periods ended September 30, 1999 is primarily due to increased costs
related to new patent applications and to legal costs related to the patent
interference and litigation associated with HMR and RPR.

    The net of interest income, interest (expense) and other income (expense)
was ($2,902,000) and ($7,727,000) for the three and nine months ended
September 30, 1999, respectively, compared to ($932,000) and ($2,716,000),
respectively, for the same periods in 1998. The increase in expense for the
three and nine month periods ended September 30, 1999 is primarily the result of
increased interest expense related to Sepracor's 6 1/4% Convertible Subordinated
Debentures due 2005 issued in February 1998 and the 7% Convertible Subordinated
Debentures due 2005, issued in December 1998, offset in part by an increase in
interest income due to a higher average daily cash balance available for
investment in 1999.

    Equity in loss of investees was $0 and $2,509,000 for the three and nine
months ended September 30, 1999, respectively, compared to $600,000 and
$1,846,000, respectively, for the same periods in 1998. The decrease for the
three month period ended September 30, 1999 is due to Sepracor no longer
recognizing Versicor losses as a result of Sepracor's change from the equity
method of accounting to the cost method of accounting as of May 1999. The
increase for the nine month period ended September 30, 1999 is due to Sepracor's
recognition of HemaSure losses in 1999 partially offset by the recognition of
less Versicor losses in 1999.

    Minority interest in subsidiary from continuing operations resulted in a
decrease to consolidated net loss of $362,000 and $910,000 for the three and
nine months ended September 30, 1999, respectively, compared to $134,000 and
$291,000, respectively, for the same periods in 1998. The fluctuation in
minority interest is the result of BioSphere's fluctuation in net loss and
discontinued operations (net of minority interests) through the second quarter
of 1999.

    Net loss from discontinued operations was $0 and $345,000 for the three and
nine months ended September 30, 1999, respectively, compared to $458,000 and
$442,000, respectively, for the same period in 1998.

LIQUIDITY AND CAPITAL RESOURCES

    Cash and cash equivalents plus marketable securities totaled $377,798,000 at
September 30,1999, compared to $499,598,000 at December 31, 1998.

                                       14
<PAGE>
    The net cash used in operating activities for the nine months ended
September 30, 1999 was $115,617,000. The net cash used in operating activities
includes a net loss of $122,675,000 adjusted by non-cash charges of $6,815,000.
Accounts receivable increased by $2,143,000 due primarily to sales of Xopenex.
Inventory increased by $5,814,000 primarily due to Sepracor's recording of
Xopenex inventories in 1999. Accounts payable decreased by $2,097,000 due to the
timing of cash disbursements made. Accrued expenses increased by $12,499,000 due
primarily to increased research and development activities.

    The net cash used in investing activities for the nine months ended
September 30, 1999 was $160,883,000. Cash was invested primarily in net
purchases of marketable securities of $142,964,000, purchases of property and
equipment of $5,567,000 and an investment of $2,000,000 in HemaSure.
Additionally, an investment of $10,000,000 in cash and 100,000 shares of issued
Sepracor common stock was made for the purchase of intangible assets.

    The net cash provided by financing activities for the nine months ended
September 30, 1999 was $2,202,000. Sepracor received $5,304,000 in net proceeds
from the issuance of common stock. Sepracor paid Versicor $500,000 under a
promissory note agreement and BioSphere used $2,458,000 primarily to repay its
bank loans.

    We believe that existing cash and investment securities, and anticipated
cash from our current product sales, and collaboration and licensing agreements
will be sufficient to support our existing operations for the near term.
Sepracor's actual future cash requirements, however, will depend on many
factors, including future product sales, the progress, number and breadth of
clinical trials and discovery programs, and the achievement of milestones under
collaboration agreements. The Company's forecast of the period of time through
which its financial resources will be adequate to support its operations is
forward-looking information, and, as such, actual results may vary.

    In December 1998, Sepracor signed a license agreement (the "Lilly
(R)-Fluoxetine Agreement") with Eli Lilly and Company ("Lilly") giving Lilly
exclusive worldwide rights to Sepracor's patents covering (R)-fluoxetine, which
is a modified form of an active ingredient found in Prozac(R). Under the terms
of the Lilly (R)-Fluoxetine Agreement, and subject to approval under the Hart
Scott Rodino Antitrust Improvements Act of 1976, as amended (the "HSR Act"),
Sepracor will receive an initial milestone payment and license fee of
$20,000,000, which will be recorded as revenue in accordance with the terms of
the agreement. Additional milestone payments of up to $70,000,000 will be made
based on the progression of (R)-fluoxetine through development. In addition,
Sepracor will receive royalties on (R)-fluoxetine worldwide sales, if any,
beginning at product launch. Under the HSR Act, Sepracor has received a request
from the Federal Trade Commission for additional information in connection with
the Lilly (R)-Fluoxetine Agreement. Sepracor plans to fully respond to the
request.

NEW ACCOUNTING PRONOUNCEMENTS

    During 1998, the Financial Accounting Standards Board ("FASB") issued
Statement of Financial Accounting Standard ("SFAS") No. 133 "Accounting for
Derivative Instruments and Hedging Activities." SFAS No. 133 was not required to
be implemented by the Company until fiscal year 2000. In June 1999, the FASB
issued SFAS No. 137, "Accounting for Derivative Instruments and Hedging
Activities--Deferral of the Effective Date of FASB Statement No. 133--An
Amendment of FASB Statement No. 133." SFAS No. 137 delayed the original
implementation date of SFAS No. 133 by one year. The Company will continue to
evaluate any potential impact this standard may have on its consolidated
financial statements.

FACTORS AFFECTING FUTURE OPERATING RESULTS

    Certain of the information contained in this Quarterly Report on Form 10-Q,
including information with respect to the safety, efficacy and potential
benefits of Sepracor's improved chemical entities, or ICEs, under development,
the scope of patent protection with respect to these products and Sepracor's
ability to market and sell its products successfully and information with
respect to the other plans and strategy for

                                       15
<PAGE>
Sepracor's business and the business of the subsidiaries and certain affiliates
of Sepracor, consists of forward-looking statements. Important factors that
could cause actual results to differ materially from the forward-looking
statements include the following:

    SEPRACOR HAS NEVER BEEN PROFITABLE AND MAY NOT BE ABLE TO GENERATE REVENUES
SUFFICIENT TO ACHIEVE PROFITABILITY.

    Sepracor has not been profitable since inception, and it is possible that it
will not achieve profitability. Sepracor incurred net losses applicable to
common shares on a consolidated basis of approximately $122,675,000 for the nine
month period ended September 30, 1999 and $93,433,000 for the year ended
December 31, 1998. Sepracor expects to continue to incur operating and capital
expenditures. As a result, it will need to generate significant revenues to
achieve and maintain profitability. Sepracor cannot assure you that it will
achieve significant revenues or that it will ever achieve profitability. Even if
Sepracor does achieve profitability, it cannot assure you that it can sustain or
increase profitability on a quarterly or annual basis in the future. If revenues
grow more slowly than Sepracor anticipates or if operating expenses exceed
Sepracor's expectations or cannot be adjusted accordingly, Sepracor's business,
results of operations and financial conditions will be materially and adversely
affected.

    SEPRACOR WILL BE REQUIRED TO EXPEND SIGNIFICANT RESOURCES FOR RESEARCH,
DEVELOPMENT, TESTING AND REGULATORY APPROVAL OF ITS DRUGS UNDER DEVELOPMENT AND
THESE DRUGS MAY NOT BE DEVELOPED SUCCESSFULLY.

    Sepracor is focused on the development of ICEs. Most of Sepracor's ICEs are
still undergoing clinical trials or are at the early stages of development.
Sepracor's drugs may not provide greater benefits or fewer side effects than the
original versions of these drugs and its research efforts may not lead to the
discovery of new drugs with improved characteristics. All of Sepracor's drugs
under development will require significant additional research, development,
preclinical and clinical testing, regulatory approval and a commitment of
significant additional resources prior to their commercialization. Sepracor's
potential products may not:

    - be developed successfully;

    - be proven safe and efficacious in clinical trials;

    - offer therapeutic or other improvements over comparable drugs;

    - meet applicable regulatory standards;

    - be capable of being produced in commercial quantities at acceptable costs;
      or

    - be successfully marketed or sold.

    IF SEPRACOR FAILS TO ADEQUATELY PROTECT ITS INTELLECTUAL PROPERTY RIGHTS OR
FACES A CLAIM OF INTELLECTUAL PROPERTY INFRINGEMENT BY A THIRD PARTY, THEN IT
COULD LOSE VALUABLE INTELLECTUAL PROPERTY RIGHTS OR BE LIABLE FOR SIGNIFICANT
DAMAGES.

    Sepracor's success depends in part on its ability to obtain and maintain
patents, protect trade secrets and operate without infringing upon the
proprietary rights of others. In the absence of patent and trade secret
protection, competitors may adversely affect Sepracor's business by
independently developing and marketing substantially equivalent products and
technology and preventing Sepracor from marketing its products. It is also
possible that Sepracor could incur substantial costs in litigation if it is
required to defend itself in patent suits brought by third parties, or if
Sepracor is required to initiate litigation against others to protect its
intellectual property rights.

    Sepracor has filed various patent applications covering the composition of,
and the methods of using, single-isomer or active-metabolite forms of various
compounds for specific applications. However,

                                       16
<PAGE>
Sepracor may not be issued patents in respect of the patent applications already
filed or that it may file in the future. Moreover, the patent position of
companies in the pharmaceutical industry generally involves complex legal and
factual questions, and recently has been the subject of much litigation.
Therefore, any patents Sepracor has obtained, or obtains in the future, might be
challenged, invalidated or circumvented.

    Sepracor's ability to commercialize successfully any ICE will largely depend
upon its ability to obtain and maintain use patents of sufficient scope to
prevent third parties from developing similar or competitive products. Third
parties, typically drug companies, hold patents or patent applications covering
the composition of matter for most of the ICEs for which Sepracor has use
patents or patent applications. In each such case, unless Sepracor has or
obtains a license agreement, Sepracor may not be permitted to commercialize the
ICE until the expiration of these third-party patents. Licenses may not be
available to Sepracor on acceptable terms, if at all. In addition, it would be
costly to contest the validity of a third-party patent or defend any claim that
Sepracor infringes a third-party patent. Moreover, litigation involving
third-party patents may not be resolved in Sepracor's favor.

    SEPRACOR HAS LIMITED SALES AND MARKETING EXPERIENCE AND EXPECTS TO INCUR
SIGNIFICANT EXPENSES IN DEVELOPING A SALES FORCE. IN ADDITION, SEPRACOR'S
LIMITED SALES AND MARKETING EXPERIENCE MAY RESTRICT ITS SUCCESS IN
COMMERCIALIZING ITS PRODUCTS.

    Sepracor currently has very limited sales and marketing experience. If
Sepracor successfully develops and obtains regulatory approval for the products
it is currently developing, Sepracor expects to license some of them to large
pharmaceutical companies and market and sell others through its direct specialty
sales forces or through other arrangements, including co-promotion arrangements.
Sepracor has established a direct sales force to market its single isomer form
of albuterol, Xopenex. As Sepracor begins to enter into co-promotion
arrangements or market and sell additional products directly, Sepracor will need
to significantly expand its sales force. Sepracor expects to incur significant
expense in expanding its direct sales force and Sepracor's limited experience
may restrict its success in commercializing its products.

    Sepracor's ability to realize significant revenues from direct marketing and
sales activities depends on its ability to attract and retain qualified sales
personnel in the pharmaceutical industry and competition for these people is
intense. If Sepracor is unable to attract and retain qualified sales personnel,
Sepracor will not be able to successfully expand its marketing and direct sales
force on a timely or cost effective basis. Further, Sepracor's sales and
marketing efforts may not be successful, and the need to comply with FDA limits
on drug product marketing, including limits on claims of comparative safety or
efficacy, may inhibit the effectiveness of its marketing efforts. In addition,
Sepracor will need to enter into co-promotion arrangements with third parties
where its own direct sales force is neither well situated nor large enough to
achieve maximum penetration in the market. Sepracor may not be successful in
entering into any co-promotion arrangements, and the terms of any co-promotion
arrangements may not be favorable to Sepracor.

    SALES THROUGH THIRD PARTIES COULD BE LESS PROFITABLE THAN DIRECT SALES AND
THIRD PARTIES MAY SELL COMPETING PRODUCTS.

    Our current sales and marketing operation is not sufficient to achieve our
desired level of sales for Xopenex. We have entered into an agreement with a
third party to assist our selling efforts for Xopenex and we may seek additional
contract sales assistance. Sales through a third party sales force could be less
profitable than direct sales.

    IF SEPRACOR'S PRODUCTS DO NOT RECEIVE GOVERNMENT APPROVAL, THEN SEPRACOR
WILL NOT BE ABLE TO COMMERCIALIZE THEM.

    The U.S. Food and Drug Administration, or FDA, and similar foreign agencies
must approve the marketing and sale of pharmaceutical products developed by
Sepracor or its development partners. These agencies impose substantial
requirements on the manufacture and marketing of drugs. Sepracor's failure

                                       17
<PAGE>
to obtain regulatory approval on a timely basis and any unanticipated
significant expenditures on preclinical and clinical studies could adversely
affect the funds Sepracor will require to advance its products to
commercialization and the timing of the commercial introduction of, or its
ability to market and sell, its products. The regulatory process to obtain
marketing approval requires clinical trials of a product to establish its safety
and efficacy. Problems that may arise during clinical trials include:

    - results of clinical trials may not be consistent with pre-clinical study
      results;

    - results from later phases of clinical trials may not be consistent with
      the results from earlier phases; and

    - products may not be shown to be safe and efficacious.

    The clinical trial and regulatory approval process can take many years and
require substantial expenditures. Sepracor may not obtain regulatory approval
for products on a timely basis, if at all. With respect to certain of Sepracor's
ICEs, Sepracor has been able to shorten the regulatory approval process by
relying on the parent drug's preclinical and clinical toxicology data already on
file with the FDA. However, it is possible that the FDA will not permit Sepracor
to use this strategy in the future. Accordingly, Sepracor may be required to
expend significant resources to complete preclinical and clinical studies for
its other ICEs, which would significantly delay the regulatory approval process.
Even if the FDA or a similar foreign agency grants Sepracor regulatory approval
of a product, the approval may be subject to limitations on the indicated uses
for which the product may be marketed or contain requirements for costly
post-marketing follow-up studies. Moreover, if Sepracor fails to comply with
applicable regulatory requirements, it may be subject to fines, suspension or
withdrawal of regulatory approvals, product recalls, seizure of products,
operating restrictions and criminal prosecution.

    IF SEPRACOR DOES NOT MAINTAIN CURRENT GOOD MANUFACTURING PRACTICES, THEN THE
FDA COULD REFUSE TO APPROVE MARKETING APPLICATIONS. SEPRACOR DOES NOT HAVE THE
CAPABILITY TO MANUFACTURE, IN SUFFICIENT QUANTITIES, ALL OF THE PRODUCTS WHICH
MAY BE APPROVED FOR SALE, AND DEVELOPING AND OBTAINING THIS CAPABILITY WILL BE
TIME CONSUMING AND EXPENSIVE.

    The FDA and other regulatory authorities require that Sepracor's products be
manufactured according to their Good Manufacturing Practices standards.
Sepracor's failure to maintain current Good Manufacturing Practices compliance
and/or scale up its manufacturing processes could lead to refusal by the FDA to
approve marketing applications. Failure in either respect could also be the
basis for action by the FDA to withdraw approvals previously granted and for
other regulatory action.

    Sepracor's failure to increase its manufacturing capabilities may mean that
even if it develops new products, it may not be able to produce them. Sepracor
currently operates a manufacturing plant that is compliant with current Good
Manufacturing Practices that Sepracor believes can produce commercial quantities
of Xoponex and support the production of Sepracor's other possible products in
amounts needed for its clinical trials. However, Sepracor will not have the
capability to manufacture in sufficient quantities all of the products which may
be approved for sale. Accordingly, Sepracor may be required to spend money to
expand its current manufacturing facility, build an additional manufacturing
facility or contract the production of these drugs to third-party manufacturers.

    Sepracor currently has a supply contract with ChiRex that commits Sepracor
to purchase through December 31, 2001 all of its annual requirements of those
drugs that it will market directly through its specialty sales force, provided
ChiRex meets certain pricing, supply and quality control conditions. If ChiRex
experiences delays or difficulties in producing, packaging or delivering the
drugs, market introduction and subsequent sales of the drugs that Sepracor
markets through its specialty sales force could be adversely affected. Under
this supply agreement, however, Sepracor retains the right to manufacture
commercial quantities of its drugs in its Nova Scotia manufacturing plant.

                                       18
<PAGE>
    SEPRACOR COULD BE EXPOSED TO SIGNIFICANT LIABILITY CLAIMS IF IT IS UNABLE TO
OBTAIN INSURANCE AT ACCEPTABLE RATES OR OTHERWISE PROTECT AGAINST POTENTIAL
LIABILITY CLAIMS.

    Sepracor may be subjected to product liability claims that are inherent in
the testing, manufacturing, marketing and sale of human health care products.
These claims could expose Sepracor to significant liabilities that could prevent
or interfere with its product commercialization efforts. Product liability
claims could require Sepracor to spend significant time and money in litigation
or to pay significant damages. Although Sepracor maintains limited product
liability insurance coverage for both the clinical trials and commercialization
of Sepracor's products, it is possible that Sepracor will not be able to obtain
further product liability insurance on acceptable terms, if at all, and that
insurance subsequently obtained will not provide adequate coverage against all
potential claims.

    THE DEVELOPMENT AND COMMERCIALIZATION OF SEPRACOR'S PRODUCTS COULD BE
DELAYED OR TERMINATED IF SEPRACOR'S COLLABORATIVE PARTNERS TERMINATE, OR FAIL TO
PERFORM THEIR OBLIGATIONS UNDER THEIR AGREEMENTS WITH SEPRACOR.

    Sepracor's ability to commercialize certain drugs that Sepracor develops is
likely to depend significantly on its continued ability to enter into
collaborative agreements with pharmaceutical companies to fund all or part of
the costs to complete the development of these drugs and to manufacture and/or
market these drugs. In each of Sepracor's collaborative arrangements and, to the
extent that it enters into additional collaborative arrangements, Sepracor
depends upon the efforts of its collaboration partners, and these efforts may
not be successful. If any of Sepracor's collaboration partners were to breach or
terminate their agreements with Sepracor, or fail to perform their obligations
to Sepracor in a timely manner, the development and commercialization of the
products could be delayed or terminated. Any delay or termination of this type
could have a material, adverse effect on Sepracor's financial condition and
results of operations because Sepracor may be required to expend additional
funds to bring its products to commercialization, and milestone or royalty
payments from collaborative partners or revenue from product sales, if any,
could be delayed or terminated. Any failure or inability by Sepracor to perform
some of its obligations under a collaborative agreement could reduce or
extinguish the benefits to which Sepracor is otherwise entitled under the
agreement.

    Currently, Sepracor has a number of collaboration agreements. Sepracor has
licensed to Hoechst Marion Roussel its U.S. patent rights to fexofenadine, which
is marketed by Hoechst Marion Roussell as Allegra(R), and is entitled to receive
royalties on all U.S. sales of Allegra when the patent on the parent drug
expires. Sepracor has also licensed its worldwide patent rights in desloratadine
to Schering-Plough, Ltd., pursuant to which it is entitled to receive royalties
from Schering-Plough, Ltd. upon the initial sale of the product. Sepracor has
entered into an agreement with Janssen Pharmaceutica N.V., a wholly owned
subsidiary of Johnson & Johnson, with respect to norastemizole. On May 14, 1999,
Sepracor announced that Janssen had elected not to exercise its option to
co-promote norastemizole. Sepracor has exclusively licensed its rights in a
compound known as norcisapride to Janssen, and may be entitled to receive
royalties on product sales, if any, beginning upon the first commercial sale.
These royalties will escalate upon achievement of sales volume milestones.
Sepracor has exclusively licensed its (R)-fluoxetine rights to Eli Lilly and
Company, and, in addition to up front license and development milestone
payments, is entitled to receive royalties on product sales beginning upon the
first commercial sale. This agreement will be effective on the next business day
following the expiration or earlier termination of the notice and waiting period
under the Hart Scott Rodino Act of 1976. Under the Hart Scott Rodino Act of
1976, Sepracor has received a request from the Federal Trade Commission for
additional information in connection with the (R)-Fluoxetine Agreement.

    Sepracor cannot assure you that it will be able to enter into collaborative
agreements for ICEs in the future or that the terms of the collaborative
agreements, if any, will be favorable to Sepracor. The inability

                                       19
<PAGE>
to enter into collaborative agreements in the future could delay or preclude the
development, manufacture and/or marketing of some of Sepracor's drugs and could
have a material adverse effect on Sepracor's financial condition and results of
operations because:

    - Sepracor may be required to expend additional funds to advance the drugs
      to commercialization;

    - revenue from product sales could be delayed; or

    - Sepracor may elect not to commercialize the drugs.

    SEPRACOR HAS SIGNIFICANT LONG-TERM DEBT AND IT MAY NOT BE ABLE TO MAKE
INTEREST OR PRINCIPAL PAYMENTS WHEN DUE.

    As of September 30, 1999, Sepracor's total long-term debt was approximately
$491,651,000 and its stockholders' deficit was approximately $104,296,000.
Neither the debentures issued in February 1998 nor the debentures issued in
December 1998 restrict Sepracor's ability, or its subsidiaries' ability, to
incur additional indebtedness, including debt that ranks senior to these
debentures. Additional indebtedness of Sepracor may rank senior to or on parity
with these debentures in certain circumstances. Sepracor's ability to satisfy
its obligations will depend upon Sepracor's future performance, which is subject
to many factors, including factors beyond its control. It is possible that
Sepracor will be unable to meet its debt service requirements on any of its
outstanding debentures. Moreover, Sepracor may be unable to repay the 6 1/4%
debentures or 7% debentures at maturity or otherwise in accordance with the debt
instruments.

    IF SUFFICIENT FUNDS TO FINANCE SEPRACOR'S BUSINESS ARE NOT AVAILABLE TO
SEPRACOR WHEN NEEDED OR ON ACCEPTABLE TERMS, THEN SEPRACOR MAY BE REQUIRED TO
DELAY, SCALE BACK, ELIMINATE OR ALTER ITS STRATEGY FOR ITS PROGRAMS.

    Sepracor may require additional funds for its research and product
development programs, operating expenses, the pursuit of regulatory approvals,
and the expansion of Sepracor's production, sales and marketing capabilities.
Historically, Sepracor has satisfied its funding needs through collaborative
arrangements with corporate partners, equity or debt financing. Sepracor cannot
assure you that these funding sources will be available to it when needed in the
future, or, if available, will be on terms acceptable to Sepracor. Insufficient
funds could require Sepracor to delay, scale back or eliminate certain of its
research and product development programs or to license third parties to
commercialize products or technologies that Sepracor would otherwise develop or
commercialize itself. Sepracor's cash requirements may vary materially from
those now planned because of factors including:

    - increased research and development expenses;

    - patent developments;

    - relationships with collaborative partners;

    - the FDA regulatory process; and

    - Sepracor's capital requirements.

    SEPRACOR EXPECTS TO FACE INTENSE COMPETITION AND ITS COMPETITORS HAVE
GREATER RESOURCES AND CAPABILITIES THAN SEPRACOR HAS. DEVELOPMENTS BY OTHERS MAY
RENDER SEPRACOR'S PRODUCTS OR TECHNOLOGIES OBSOLETE OR NONCOMPETITIVE.

    Sepracor expects to encounter intense competition in the sale of its future
products. If Sepracor is unable to compete effectively, its financial condition
and results of operations could be materially adversely affected because
Sepracor may use its financial resources to seek to differentiate itself from
its competition and because Sepracor may not achieve its product revenue
objectives. Many of Sepracor's competitors and potential competitors, which
include pharmaceutical companies, biotechnology firms,

                                       20
<PAGE>
universities and other research institutions, have substantially greater
resources, manufacturing and marketing capabilities, research and development
staff and production facilities than Sepracor has. The fields in which Sepracor
competes are subject to rapid and substantial technological change. Sepracor's
competitors may be able to respond more quickly to new or emerging technologies
or to devote greater resources to the development, manufacture and marketing of
new products and/or technologies than Sepracor can. As a result, any products
and/or technologies that Sepracor may develop may become obsolete or
non-competitive before Sepracor can recover expenses incurred in connection with
their development.

    FLUCTUATIONS IN THE DEMAND FOR PRODUCTS, THE TIMING OF COLLABORATIVE
ARRANGEMENTS, EXPENSES AND THE RESULTS OF OPERATIONS OF SEPRACOR'S SUBSIDIARIES
WILL CAUSE FLUCTUATIONS IN SEPRACOR'S QUARTERLY OPERATING RESULTS, WHICH COULD
CAUSE VOLATILITY IN ITS STOCK PRICE.

    Sepracor's quarterly operating results are likely to fluctuate
significantly, which could cause our stock price to be volatile. These
fluctuations will depend on factors which include:

    - the timing of collaborative agreements for Sepracor's pharmaceutical
      development candidates and development costs for those pharmaceuticals;

    - the timing of product sales and market penetration;

    - the timing of operating expenses, including marketing expenses and the
      costs of expanding and maintaining a direct sales force;

    - the timing of significant orders for the products of BioSphere; and the
      losses of HemaSure and Versicor, to the extent Sepracor is required to
      recognize these losses.

                                       21
<PAGE>
YEAR 2000 ISSUE

    The year 2000 issue is the result of computer programs being written using
two digits (rather than four) to define the applicable year. Any of Sepracor's
programs that have time-sensitive software may recognize a date using "00" as
the year 1900 rather than the year 2000, which could result in miscalculation or
system failures. In 1996, Sepracor began a comprehensive project, fully
supported by senior management, to determine the risks and impacts of the Year
2000, or Y2K, computer problem on Sepracor's ability to operate into the next
century. This plan took into account Sepracor's status as a pharmaceutical
research and development company, and its transition to a fully-developed
pharmaceutical company, with research and development, manufacturing,
distribution and sales functions. The project relates to the following areas:
(i) Sepracor's internal systems (including information technology systems, such
as financial systems, and non-information technology systems, such as telephones
and facilities); and (ii) the readiness of Sepracor's vendors.

    Department managers in every business area participated in the project,
under the leadership of a Y2K Project Manager. Sepracor began this project in
1996 so as to incorporate Y2K readiness into its business strategy, and to
identify and replace non-compliant systems and procedures as part of its normal
operating plan and budget.

    Y2K State of Readiness: The term "Y2K compliant" as used herein means that
all Sepracor systems, procedures, and products will correctly identify and
process without error all dates, including those calculations which reference
leap years, and one or more centuries.

    Sepracor has completed its assessment of the impact of Y2K on its present
and future operations, and has identified computer and microprocessor based
systems, both hardware and software driven, which could potentially be affected
by the turnover to the next century. These components and systems have been
tested for Y2K compliance. Those systems which required replacement or
modification have been addressed and re-tested. At this point all systems are
fully compliant.

    Sepracor's goal of achieving full compliance on its internal systems was
achieved in July 1999. This compliance was fully tested when a complete
integrated systems test of all our business systems, including those which
access outside services, was performed. This test involved our voice as well as
data systems, and all test criteria were met successfully.

    We have completed the process of reviewing Y2K Compliance certifications
that were requested from our key suppliers earlier this year. At this time, we
are confident that our key suppliers are either fully compliant, or plan to be
prior to December 31, 1999. We have also completed a review of the outsourcing
companies who package, test and distribute our products and found them to be Y2K
compliant.

    Y2K Costs: Costs related to Year 2000 issues are funded through the
information technology operating budget and represent an immaterial portion of
this IT budget. Spending associated with Y2K issues has not caused us to defer
any other IT projects.

    To date, Sepracor has spent approximately $425,000 to retrofit or replace
computer-based systems, which were identified as lacking compliance. This
included the migration of all of Sepracor's desktop computers to an operating
status Sepracor considers to be Y2K certified, through software upgrades or full
system replacements. Sepracor's key telecommunications systems were also
upgraded and/or replaced. These costs have been minimal due to the fact that Y2K
compliance has been a prerequisite to all new systems acquisitions and
maintenance upgrades. Sepracor expects that it will not incur any significant
additional costs associated with its Y2K readiness efforts.

    Y2K Contingency Plans: The Company has completed a contingency plan which
will enable all of the essential aspects of our business to continue to function
in the event of a significant Y2K systems problem.

    Y2K Risks: Sepracor relies on third-party suppliers and service providers.
If these or other parties experience Y2K failures or malfunctions there could be
an adverse impact on the Company's ability to conduct operations, including
conducting continued pharmaceutical development efforts and manufacturing
pharmaceutical products. At this time, the Company does not anticipate this
worst case scenario to occur, nor does Sepracor anticipate any major
interruptions in its ability to provide products and services to our customers.

                                       22
<PAGE>
ITEM 3.  QUANTITATIVE AND QUALITATIVE DISCLOSURES ABOUT MARKET RISK.

MARKET RISK

    The Company's exposure to market risk from changes in interest rates and
equity prices has not changed materially from its exposure at year-end 1998.

                                       23
<PAGE>
                                    PART II
                               OTHER INFORMATION

ITEM 1. LEGAL PROCEEDINGS.

    On February 12, 1999, the Federal Trade Commission ("FTC") issued a request
for additional information or documentary materials relating to the Company's
exclusive license agreement with Eli Lilly and Company (the "Lilly Agreement").
The purpose of the request was to investigate whether or not the Lilly Agreement
constitutes a violation of Section 5 of the Federal Trade Commission Act and
Section 7 of the Clayton Act. The Company is in the process of responding to the
request. At the conclusion of its investigation, the FTC could institute
proceedings seeking to modify the Lilly Agreement or to prevent it from becoming
effective. While the Company believes that the Lilly Agreement does not
constitute a violation of the above-mentioned laws, the Company is unable to
predict the outcome of the proceeding.

    The interference declared on June 30, 1999 between Sepracor and
Rhone-Poulenc Rorer S.A. ("RPR") relating to (+)-zopiclone will be dissolved by
Sepracor's agreement with RPR of October 7, 1999, under which RPR's involved
patent application will be assigned to Sepracor. (See Note 9, Subsequent events)

    All legal proceedings between Sepracor and Hoechst Marion Roussel ("HMR")
relating to fexofenadine, including foreign litigation and the interference
between Sepracor and HMR, have been settled by Sepracor's agreement with HMR of
September 1, 1999. (See Item 2, Management's Discussion and Analysis of
Financial Condition and Results of Operations)

    HemaSure is a defendant in two lawsuits brought by Pall Corporation
("Pall"). In complaints filed in February 1996 and November 1996, Pall alleged
that HemaSure's manufacture, use and/or sale of the LeukoNet product infringes
upon three patents held by Pall. On October 14, 1996, in connection with the
first action concerning U.S. Patent No. 5,451,321 (the "321 Patent"), HemaSure
filed a motion for summary judgment of noninfringement. Pall filed a cross
motion for summary judgment of infringement at the same time. In October 1997,
the U.S. District Court of the Eastern District of New York ("EDNY") granted in
part Pall's summary judgment motion and held that the LeukoNet product infringes
a single claim from the "321 Patent. HemaSure has terminated the manufacture,
use, sale and offer for sale of the filter subject to the court's order.
HemaSure appealed the October 1997 decision to the Court of Appeals for the
Federal Circuit. In June 1999, the Court of Appeals for the Federal Circuit
determined that the LeukoNet product did not infringe the claim of the "321
patent.

    With respect to the second action concerning U.S. Patent No's. 4,952,572
(the "572 Patent") and 4,340,479 (the "479 patent"), HemaSure has answered the
complaint stating that it does not infringe any claim of the asserted patents.
Further, HemaSure has counterclaimed for declaratory judgment of invalidity,
noninfringement and unenforceability of the "572 Patent. Pall has amended its
complaint to add Lydall, Inc. ("Lydall"), whose subsidiary supplied filter media
for the LeukoNet product, as a co-defendant and has dropped its claim that the
LeukoNet product infringes the "479 patent. HemaSure has filed for summary
judgment of noninfringement, and Pall has cross-filed for summary judgment of
infringement at the same time. Lydall supported HemaSure's motion for summary
judgment of noninfringement, and has served a motion for summary judgment that
the asserted claims of the "572 Patent are invalid as a matter of law. Discovery
has been completed in the action.

    On April 5, 1999, HemaSure and COBE BCT, Inc. ("COBE BCT") filed a complaint
for declaratory relief against Pall in the U.S. District Court of Colorado.
HemaSure and COBE BCT seek declaratory relief that Pall's U.S. Patent No's.
4,925,572, 5,229,012, 5,344,561, 5,451,321, 5,501,795 and 5,863,436 are invalid
and not infringed by HemaSure's r\LS filter and methods of using the r\LS
filter. Pall moved to dismiss, to transfer, or, in the alternative, to stay this
action and HemaSure and COBE BCT opposed Pall's

                                       24
<PAGE>
motion. On July 16, 1999, the U.S. District Court of Colorado denied Pall's
motion to transfer and on September 30, 1999 the court denied Pall's motion to
dismiss. Discovery is now proceeding.

    On April 23, 1999, Pall filed a complaint against HemaSure and COBE BCT in
the EDNY alleging that HemaSure's r\LS filter infringes Pall's "572 patent,
tortuously interfered and unfairly competed with Pall's business. HemaSure was
served with the complaint on April 30, 1999. On May 19, 1999, Pall filed an
amended complaint in the EDNY adding Sepracor, COBE Laboratories, Inc. ("COBE
LABS"), Gambro, A.B. as defendants and alleging that Sepracor induced and
contributed to HemaSure's alleged infringement of Pall's "572 patent, and
allegedly tortuously interfered and unfairly competed with Pall's business.
Sepracor was served with the amended complaint on June 1, 1999. Sepracor,
HemaSure and COBE LABS have moved to dismiss, transfer, or stay the action, and
Pall has opposed the motion.

    HemaSure believes, based on advice of its legal counsel, that a properly
informed court should conclude that the manufacture, use and/or sale by HemaSure
or its customers of the LeukoNet product and the r\LS product did not infringe
any valid enforceable claim of the Pall patents. However, there can be no
assurance that HemaSure will prevail in the pending litigation, and an adverse
outcome in a patent infringement action would have a material adverse effect on
HemaSure's financial condition and future business and operations.

    Sepracor believes, based on advice of its legal counsel, that a properly
informed court should conclude that Pall's suit against Sepracor should be
dismissed. However, there can be no assurance that this suit will be dismissed
or that Sepracor will prevail in the pending litigation.

ITEMS 2 - 5 NONE

ITEM 6. EXHIBITS AND REPORTS ON FORM 8-K

    The Exhibit Index immediately preceding the exhibits is incorporated by
reference.

    a)  Exhibits:

           10.1  Amended and Restated 1991 Stock Option Plan

           10.2  1999 Director Stock Option Plan

           10.3  Assignment Agreement By and Between The Registrant and
                 Georgetown University, Dated August 25, 19999

           10.4  Registration Rights Agreement, Dated as of August 25, 1999, By
                 and Between The Registrant and Georgetown University

           27.1  Financial Data Schedule

    b)  Reports on Form 8-K

    None

                                       25
<PAGE>
                                   SIGNATURES

    Pursuant to the requirements of the Securities Exchange Act of 1934, the
registrant has duly caused this report to be signed on its behalf by the
undersigned thereunto duly authorized.

<TABLE>
<S>                                                    <C>  <C>
                                                       SEPRACOR INC.

Date: November 12, 1999                                     /s/ TIMOTHY J. BARBERICH
                                                            ----------------------------
                                                            Timothy J. Barberich
                                                            Chairman and
                                                            Chief Executive Officer
                                                            (Principal Executive Officer)

Date: November 12, 1999                                     /s/ ROBERT F. SCUMACI
                                                            ----------------------------
                                                            Robert F. Scumaci
                                                            Senior Vice President
                                                            of Finance and Administration
                                                            (Principal Accounting Officer)
</TABLE>

                                       26
<PAGE>
                                 EXHIBIT INDEX

<TABLE>
<CAPTION>
      EXHIBITS:
       NUMBER                                   DESCRIPTION
---------------------                           -----------
<S>                     <C>
 10.1                   Amended and Restated 1991 Stock Option Plan

 10.2                   1999 Director Stock Option Plan

 10.3                   Assignment Agreement By and Between The Registrant and
                        Georgetown University, Dated August 25, 1999

 10.4                   Registration Rights Agreement, Dated as of August 25, 1999,
                        By and Between The Registrant and Georgetown University

 27.1                   Financial Data Schedule
</TABLE>