Exhibit 4.4




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


                                  HEMASURE INC.

                                       AND

                                  SEPRACOR INC.

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





                                WARRANT AGREEMENT


                         Dated as of September 15, 1998




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728537.3

<PAGE>


          WARRANT  AGREEMENT,  dated as of September 15, 1998 (the "Agreement"),
between HEMASURE INC., a Delaware corporation ("HemaSure"), and SEPRACOR INC., a
Delaware corporation (the "Holder").


                              W I T N E S S E T H:

          WHEREAS,  HemaSure  and the Holder are parties to a  Revolving  Credit
Arrangement  (the "RCA") pursuant to which the Holder has guaranteed the payment
by the Company of all unpaid  balances  outstanding  under the RCA at the end of
the term of the RCA; and

          WHEREAS,  in  consideration  of the Holder's  guarantee under the RCA,
HemaSure  agreed  to issue to the  Holder  1,700,000  warrants  (individually  a
"Warrant," and collectively,  the "Warrants"), to purchase up to an aggregate of
1,700,000 shares of common stock, $.01 par value per share, of HemaSure ("Common
Stock"), upon the terms and conditions as set forth below.

          NOW, THEREFORE, in consideration of these premises, and for other good
and  valuable  consideration,  the  receipt and  sufficiency  of which is hereby
acknowledged,  the  parties  hereto  agree as follows:

          1.  Grant.  The Holder is hereby  granted  the right to  purchase  (i)
1,000,000  shares of Common Stock,  at an exercise price of $0.69 per share (the
"Exercise Price") of Common Stock, at any time prior to 5:00 p.m., New York City
time on September  14, 2003,  and (ii) 700,000  shares of Common  Stock,  at the
Exercise  Price,  at any time  following  the date,  if any,  that the Company's
indebtedness for principal amounts borrowed under the RCA exceeds $3,000,000, in
each case, subject to the terms and conditions of this Agreement.

          2.  Warrant   Certificate.   The  warrant  certificate  (the  "Warrant
Certificate")  to be delivered  pursuant to this Agreement  shall be in the form
set forth in  Exhibit  A  attached  hereto,  and made a part  hereof,  with such
appropriate  insertions,  omissions,  substitutions,  and  other  variations  as
required or permitted by this Agreement.

          3. Exercise of Warrants. The Warrants are exercisable at the aggregate
Exercise Price for the number of Warrants so exercised at any time prior to 5:00
p.m. New York City time on September 14, 2003, subject to adjustment as provided
in Section 7 hereof. Payment of such Exercise Price shall be made, at the option
of the Holder  specified in its notice of exercise,  (i) by wire  transfer or by
certified  or  official  bank  check  payable  to the  order of the  Company  in
immediately  available funds in lawful money of the United States of America; or
(ii) by reducing the number of shares of Common Stock  issuable to the Holder by
a number of shares of Common Stock that have a value equal to the Exercise Price
which otherwise  would have been paid. For the purpose of any exercise  pursuant
to the previous sentence, the value of a share of Common Stock shall be the last
reported sale price of the Common Stock on the OTC Bulletin  Board, or any other
interdealer  quotation  system  on  which  the  Common  Stock  is  included  for
quotation,  or, if none,  the fair  market  value of such  shares as  reasonably
determined by the Board of Directors of the Company. Upon surrender of a Warrant
Certificate  with the  annexed  Form of  Election  to  Purchase  duly  executed,
together  with  payment of the  Exercise  Price for the  shares of Common  Stock
purchased,  if applicable,  at HemaSure's principal offices located at 140 Locke
Drive,  Marlborough,  MA  01752,  the  Holder  shall be  entitled  to  receive a
certificate or certificates for the shares of Common

                                       -1-
728537.3

<PAGE>



Stock so purchased.  The purchase rights represented by the Warrant  Certificate
are  exercisable at the option of the Holder  thereof,  in whole or in part (but
not as to fractional shares of the Common Stock underlying the Warrants), but in
no  event  for less  than  25,000  shares  at any one  time.  In the case of the
purchase  of less  than all the  shares of Common  Stock  purchasable  under any
Warrant  Certificate,  HemaSure shall cancel said Warrant  Certificate  upon the
surrender  thereof and shall  execute and deliver a new Warrant  Certificate  of
like tenor for the balance of the shares of Common Stock purchasable thereunder.

          4. Issuance of  Certificates.  Upon the exercise of the Warrants,  the
issuance  of  certificates  for  shares  of  Common  Stock or other  securities,
properties or rights  underlying  such Warrants  shall be made forthwith (and in
any event within ten (10) business days thereafter) without charge to the Holder
including,  without  limitation,  any tax which may be payable in respect of the
issuance thereof,  and such  certificates  shall be issued in the name of, or in
such names as may be directed by, the Holder thereof;  provided,  however,  that
HemaSure shall not be required to pay any tax which may be payable in respect of
any transfer involved in the issuance and delivery of any such certificates in a
name other than that of the Holder,  and HemaSure shall not be required to issue
or deliver such  certificates  unless or until the person or persons  requesting
the issuance thereof shall have paid to HemaSure the amount of such tax or shall
have established to the satisfaction of HemaSure that such tax has been paid.

          The Warrant  Certificate and the certificates  representing the Shares
shall be executed on behalf of HemaSure by the manual or facsimile  signature of
the  then  present  Chairman  or Vice  Chairman  of the  Board of  Directors  or
President or Chief  Executive  Officer or Vice  President of HemaSure  under its
corporate  seal  reproduced  thereon,  attested  to by the  manual or  facsimile
signature of the then present Secretary or Assistant Secretary of HemaSure.  The
Warrant  Certificate  shall be dated  the date of  execution  by  HemaSure  upon
initial issuance, division, exchange, substitution or transfer.

          5.  Restriction  on  Transfer of  Warrants.  The Holder of the Warrant
Certificate, by its acceptance thereof, covenants and agrees:

               (i) that the Warrants and the shares of Common Stock  issuable on
          exercise  of the  Warrants  (the  "Shares")  are being  acquired as an
          investment and not with a view to the distribution thereof;

               (ii) that it understands that neither the Warrants nor the Shares
          have been registered under the Securities Act of 1933, as amended (the
          "Securities   Act"),  in  reliance  on  an  exemption   therefrom  for
          transactions not involving any public  offering,  and that neither the
          Warrants  nor the Shares  have been  approved  or  disapproved  by the
          United States Securities and Exchange Commission (the "Commission") or
          by any other Federal or state agency;

               (iii) it understands that neither the Warrants nor the Shares can
          be  sold,  transferred  or  assigned  unless  registered  by  HemaSure
          pursuant to the  Securities Act and any  applicable  state  securities
          laws, or unless an exemption therefrom is available, and, accordingly,
          it may not be possible for the undersigned to liquidate its investment
          in the Warrants and the Shares,  and it agrees not to sell,  assign or
          otherwise  transfer or dispose of the  Warrants  or the Shares  unless
          such Warrants or Shares, as applicable,  have been so registered or an
          exemption from registration is available;


                                       -2-
728537.3

<PAGE>



               (iv) the Holder hereby  acknowledges that all documents,  records
          and books  pertaining to HemaSure's  business have been made available
          to the Holder  and the  Holder's  attorney  and/or  accountant  and/or
          representative. The Holder has had an opportunity to ask questions and
          receive  answers from HemaSure  concerning  the business and assets of
          HemaSure  and all  such  questions  have  been  answered  to the  full
          satisfaction of the Holder; and

               (v) it is an  accredited  investor,  as that term is  defined  in
          Regulation D under the Securities Act.

          6.  Securities  Act of 1933;  Legends.  Upon  exercise,  in part or in
whole,  of the Warrants,  certificates  representing  the Shares  underlying the
Warrant and any of the other  securities  issuable  upon exercise of the Warrant
(the  "Warrant  Shares")  shall bear the  following  legend only if such Warrant
Shares are not then registered pursuant to an effective  registration  statement
under the Act:

               The securities represented by this certificate have not
               been  registered  under the  Securities Act of 1933, as
               amended  (the  "Act"),  and may not be  offered or sold
               except  pursuant  to  (i)  an  effective   registration
               statement under the Act, (ii) to the extent applicable,
               Rule 144 under the Act (or any similar  rule under such
               Act  relating to the  disposition  of  securities),  or
               (iii) an opinion of counsel,  if such opinion  shall be
               reasonably  satisfactory to counsel to the issuer, that
               an  exemption  from  registration  under  such  Act  is
               available.

          7.  Subdivision  and  Combination.  In case HemaSure shall at any time
subdivide or combine the outstanding  shares of Common Stock, the Exercise Price
shall  forthwith  be  proportionately  decreased in the case of  subdivision  or
increased in the case of  combination,  and the number of shares  subject to the
Warrant shall be proportionally increased or decreased, as the case may be.

          8. Merger or  Consolidation.  In case of any consolidation of HemaSure
with,  or  merger  of  HemaSure  with,  or  merger  of  HemaSure  into,  another
corporation  (other than a consolidation  or merger which does not result in any
reclassification  or change of the  outstanding  Common Stock),  the corporation
formed by such consolidation or merger shall execute and deliver to the Holder a
supplemental warrant agreement having terms as nearly  substantively  equivalent
as practical to the terms hereof, providing that the Holder of each Warrant then
outstanding  or to be  outstanding  shall have the right  thereafter  (until the
expiration of such Warrant) to receive,  upon exercise of such warrant, the kind
and amount of shares of stock and other securities and property  receivable upon
such  consolidation  or merger,  by the Holder of the number of shares of Common
Stock of HemaSure for which such warrant might have been  exercised  immediately
prior to such consolidation,  merger,  sale or transfer.  The above provision of
this subsection shall similarly apply to successive consolidations or mergers.

          9.  Exchange and  Replacement  of Warrant  Certificates.  Each Warrant
Certificate is exchangeable  without expense,  upon the surrender thereof by the
Holder  at  the  principal  executive  office  of  HemaSure,  for a new  Warrant
Certificate  of like tenor and date  representing  in the aggregate the right to
purchase  the same number of Warrant  Shares in such  denominations  as shall be
designated by the Holder thereof at the time of such surrender.

          Upon receipt by HemaSure of evidence reasonably  satisfactory to it of
the loss, theft,  destruction or mutilation of any Warrant Certificate,  and, in
case of loss, theft or destruction, of an

                                       -3-
728537.3

<PAGE>



indemnity  agreement  reasonably  satisfactory  to it,  and upon  surrender  and
cancellation of the Warrants, if mutilated, HemaSure will make and deliver a new
Warrant Certificate of like tenor, in lieu thereof.

          10.  Elimination  of  Fractional  Interests.  HemaSure  shall  not  be
required to issue certificates  representing fractions of shares of Common Stock
upon the  exercise of the  Warrants,  nor shall it be required to issue scrip or
pay cash in lieu of  fractional  interests,  it being the intent of the  parties
that all fractional interests shall be eliminated by rounding any fraction up to
the  nearest  whole  number  of  shares  of  Common  Stock or other  securities,
properties or rights.

          11. Reservation of Securities. HemaSure shall at all times reserve and
keep  available out of its  authorized  shares of Common  Stock,  solely for the
purpose of issuance upon the exercise of the Warrants,  such number of shares of
Common Stock or other securities, properties or rights as shall be issuable upon
the exercise thereof.

          12. Notices to the Holder.  Nothing  contained in this Agreement shall
be construed as conferring upon the Holder the right to vote or to consent or to
receive notice as a stockholder in respect of any meetings of  stockholders  for
the  election  of  directors  or any  other  matter,  or as  having  any  rights
whatsoever as a stockholder of HemaSure.  If, however,  at any time prior to the
expiration of the Warrants and their exercise, any of the following events shall
occur:

               (a) HemaSure  shall take a record of the holders of its shares of
          Common Stock for the purpose of  entitling  them to receive a dividend
          or distribution  payable otherwise than in cash, or a cash dividend or
          distribution  payable  otherwise  than  out  of  current  or  retained
          earnings, as indicated by the accounting treatment of such dividend or
          distribution on the books of HemaSure;

               (b)  HemaSure  shall  offer to all of the  holders  of its Common
          Stock any additional shares of capital stock of HemaSure or securities
          convertible  into or  exchangeable  for  shares  of  capital  stock of
          HemaSure, or any option, right or warrant to subscribe therefor; or

               (c) a dissolution,  liquidation or winding up of HemaSure  (other
          than in connection with a consolidation or merger) or a sale of all or
          substantially all of its property,  assets and business as an entirety
          shall be proposed;

then, in any one or more of said events,  HemaSure  shall give written notice of
such event at least  fifteen  (15) days prior to the date fixed as a record date
or the  date  of  closing  the  transfer  books  for  the  determination  of the
stockholders   entitled  to  such   dividend,   distribution,   convertible   or
exchangeable  securities  or  subscription  rights,  or entitled to vote on such
proposed dissolution, liquidation, winding up or sale. Such notice shall specify
such record date or the date of closing the transfer  books, as the case may be.
Failure to give such notice or any defect  therein shall not affect the validity
of any action taken in connection  with the  declaration  or payment of any such
dividend,  or the issuance of any  convertible or  exchangeable  securities,  or
subscription  rights,   options  or  warrants,   or  any  proposed  dissolution,
liquidation, winding up or sale.

          13. Notices. All notices, requests,  consents and other communications
hereunder  shall be in  writing  and  shall be deemed to have been duly made and
sent when delivered,  or mailed by registered or certified mail,  return receipt
requested:

                                       -4-
728537.3

<PAGE>



               (a) If to the  Holder,  to the  address of the Holder as shown on
          the books of HemaSure; or

               (b) If to HemaSure,  to the address set forth in Section 3 hereof
          or to such other  address as HemaSure  may  designate by notice to the
          Holder.

          14. [Intentionally Omitted].

          15.  Successors.  All the covenants and  provisions of this  Agreement
shall be binding upon and inure to the benefit of HemaSure, the Holder and their
respective successors and assigns hereunder.

          16.  Termination.  This Agreement  shall  terminate in its entirety at
5:00 p.m., New York City time, on September 14, 2003.

          17. Governing Law; Submission to Jurisdiction.

          (a) This Agreement and each Warrant Certificate issued hereunder shall
be deemed to be a contract  made under the laws of the State of Delaware and for
all  purposes  shall be  construed  in  accordance  with the laws of said  State
without  giving  effect to the rules of said State  governing  the  conflicts of
laws.

          (b) HemaSure and the Holder  hereby agree that any action,  proceeding
or claim  against it arising out of, or  relating in any way to, this  Agreement
shall be brought  and  enforced in the courts of the State of Delaware or of the
United States of America for the District of Delaware,  and irrevocably  submits
to such jurisdiction,  which  jurisdiction shall be exclusive.  HemaSure and the
Holder hereby irrevocably waive any objection to such exclusive  jurisdiction or
inconvenient  forum.  Any such process or summons to be served upon HemaSure and
the Holder (at the  option of the party  bringing  such  action,  proceeding  or
claim) may be served by transmitting a copy thereof,  by registered or certified
mail, return receipt requested,  postage prepaid, addressed to it at the address
set forth in Section 15 hereof.  Such mailing shall be deemed  personal  service
and  shall  be legal  and  binding  upon the  party  so  served  in any  action,
proceeding  or  claim.  HemaSure  and  the  Holder  agree  that  the  prevailing
party(ies)  in any such action or  proceeding  shall be entitled to recover from
the other  party(ies)  all of  its/their  reasonable  legal  costs and  expenses
relating to such action or proceeding  and/or  incurred in  connection  with the
preparation therefor.

          18. Entire Agreement; Modification. This Agreement contains the entire
understanding  between the parties  hereto  with  respect to the subject  matter
hereof and may not be modified or amended except by a writing duly signed by the
party against whom enforcement of the modification or amendment is sought.

          19. Severability.  If any provision of this Agreement shall be held to
be invalid or  unenforceable,  such  invalidity  or  unenforceability  shall not
affect any other provision of this Agreement.

          20.  Captions.  The caption headings of the Sections of this Agreement
are for  convenience of reference only and are not intended,  nor should they be
construed as, a part of this Agreement and shall be given no substantive effect.


                                       -5-
728537.3

<PAGE>



          21.  Benefits of this  Agreement.  Nothing in this Agreement  shall be
construed to give to any person or corporation other than HemaSure or the Holder
any legal or equitable right, remedy or claim under this Agreement.

          22.  Counterparts.  This  Agreement  may be  executed in any number of
counterparts and each of such  counterparts  shall for all purposes be deemed to
be an original,  and such counterparts shall together constitute but one and the
same instrument.  Photocopies or facsimiles of executed copies of this Agreement
may be treated as originals.



                            [signature page follows]



                                       -6-
728537.3

<PAGE>



          IN WITNESS  WHEREOF,  the parties hereto have caused this Agreement to
be duly executed, as of the day and year first above written.

                                  HEMASURE INC.


                                  By: /s/James B. Murphy
                                      ------------------
                                      Name:    James B. Murphy
                                      Title:   Senior VP Finance and 
                                                  Administration


                                  SEPRACOR INC.


                                  By: /s/Robert Scumaci
                                      ------------------
                                      Name:    Robert Scumaci
                                      Title:   Senior VP Finance and 
                                                  Administration


                                       -7-
728537.3