|
OMB
APPROVAL
|
||
|
UNITED
STATES
SECURITIES
AND EXCHANGE COMMISSION
Washington,
D.C. 20549
|
OMB
Number:
3235-0145
Expires:
February 28, 2009
Estimated
average burden
hours
per response..............10.4
|
SCHEDULE
13G
Under
the Securities Exchange Act of 1934
|
ImmunoGen,
Inc.
|
(Name of
Issuer)
|
Common
Stock, Par Value $.01 Per
Share
|
(Title of
Class of Securities)
|
45253H101
|
(CUSIP
Number)
|
June
20, 2008
|
(Date of
Event which Requires Filing of this Statement)
Check the
appropriate box to designate the rule pursuant to which this Schedule is
filed:
¨ Rule
13d-1(b)
ý Rule
13d-1(c)
¨ Rule
13d-1(d)
* The
remainder of this cover page shall be filled out for a reporting person's
initial filing on this form with respect to the subject class of securities, and
for any subsequent amendment containing information which would alter
disclosures provided in a prior cover page.
The
information required in the remainder of this cover page shall not be deemed to
be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934
(“Act”) or otherwise subject to the liabilities of that section of the Act but
shall be subject to all other provisions of the Act (however, see the
Notes).
|
CUSIP No. 45253H101
|
13G
|
Page 2 of 10
Pages
|
|
1
|
NAMES
OF REPORTING PERSONS
I.R.S.
IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)
Ziff Asset Management,
L.P.
|
|
2
|
CHECK THE APPROPRIATE BOX IF A
MEMBER OF A GROUP (SEE
INSTRUCTIONS)
(a) o
(b) o
|
|
3
|
SEC
USE ONLY
|
|
4
|
CITIZENSHIP
OR PLACE OF ORGANIZATION
Delaware
|
|
NUMBER OF
SHARES
|
5
|
SOLE
VOTING POWER
0
|
|
BENEFICIALLY
OWNED BY
|
6
|
SHARED
VOTING POWER
7,812,500
|
|
EACH
REPORTING
|
7
|
SOLE
DISPOSITIVE POWER
0
|
|
PERSON
WITH
|
8
|
SHARED
DISPOSITIVE POWER
7,812,500
|
|
9
|
AGGREGATE
AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
7,812,500
|
|
10
|
CHECK
IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE
INSTRUCTIONS)
o
|
|
11
|
PERCENT
OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
15.4%
|
|
12
|
TYPE
OF REPORTING PERSON (SEE INSTRUCTIONS)
PN
|
|
CUSIP No. 45253H101
|
13G
|
Page 3 of 10
Pages
|
|
1
|
NAMES
OF REPORTING PERSONS
I.R.S.
IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)
PBK Holdings, Inc.
|
|
2
|
CHECK THE APPROPRIATE BOX IF A
MEMBER OF A GROUP (SEE
INSTRUCTIONS)
(a) o
(b) o
|
|
3
|
SEC
USE ONLY
|
|
4
|
CITIZENSHIP
OR PLACE OF ORGANIZATION
Delaware
|
|
NUMBER OF
SHARES
|
5
|
SOLE
VOTING POWER
0
|
|
BENEFICIALLY
OWNED BY
|
6
|
SHARED
VOTING POWER
7,812,500
|
|
EACH
REPORTING
|
7
|
SOLE
DISPOSITIVE POWER
0
|
|
PERSON
WITH
|
8
|
SHARED
DISPOSITIVE POWER
7,812,500
|
|
9
|
AGGREGATE
AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
7,812,500
|
|
10
|
CHECK
IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE
INSTRUCTIONS) o
|
|
11
|
PERCENT
OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
15.4%
|
|
12
|
TYPE
OF REPORTING PERSON (SEE INSTRUCTIONS)
CO
|
|
CUSIP No. 45253H101
|
13G
|
Page 4 of 10
Pages
|
|
1
|
NAMES
OF REPORTING PERSONS
I.R.S.
IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)
Philip B. Korsant
|
|
2
|
CHECK THE APPROPRIATE BOX IF A
MEMBER OF A GROUP (SEE
INSTRUCTIONS)
(a) o
(b) o
|
|
3
|
SEC
USE ONLY
|
|
4
|
CITIZENSHIP
OR PLACE OF ORGANIZATION
United States of
America
|
|
NUMBER OF
SHARES
|
5
|
SOLE
VOTING POWER
0
|
|
BENEFICIALLY
OWNED BY
|
6
|
SHARED
VOTING POWER
7,812,500
|
|
EACH
REPORTING
|
7
|
SOLE
DISPOSITIVE POWER
0
|
|
PERSON
WITH
|
8
|
SHARED
DISPOSITIVE POWER
7,812,500
|
|
9
|
AGGREGATE
AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
7,812,500
|
|
10
|
CHECK
IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE
INSTRUCTIONS)
o
|
|
11
|
PERCENT
OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
15.4%
|
|
12
|
TYPE
OF REPORTING PERSON (SEE INSTRUCTIONS)
IN
|
|
CUSIP No. 45253H101
|
13G
|
Page 5 of 10
Pages
|
|
1
|
NAMES
OF REPORTING PERSONS
I.R.S.
IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)
ZBI Equities, L.L.C.
|
|
2
|
CHECK THE APPROPRIATE BOX IF A
MEMBER OF A GROUP (SEE INSTRUCTIONS)
(a) o
(b) o
|
|
3
|
SEC
USE ONLY
|
|
4
|
CITIZENSHIP
OR PLACE OF ORGANIZATION
Delaware
|
|
NUMBER OF
SHARES
|
5
|
SOLE
VOTING POWER
0
|
|
BENEFICIALLY
OWNED BY
|
6
|
SHARED
VOTING POWER
7,812,500
|
|
EACH
REPORTING
|
7
|
SOLE
DISPOSITIVE POWER
0
|
|
PERSON
WITH
|
8
|
SHARED
DISPOSITIVE POWER
7,812,500
|
|
9
|
AGGREGATE
AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
7,812,500
|
|
10
|
CHECK
IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE
INSTRUCTIONS)
o
|
|
11
|
PERCENT
OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
15.4%
|
|
12
|
TYPE
OF REPORTING PERSON (SEE INSTRUCTIONS)
IA
|
Item
1. (a) Name of Issuer
ImmunoGen,
Inc.
Item
1. (b) Address of Issuer’s Principal
Executive Offices
830
Winter Street
Waltham,
MA 02451
Item
2.(a) Name of Person
Filing
This
Schedule 13G is being filed on behalf of the following persons (the “Reporting
Persons”)*:
|
(i)
|
Ziff
Asset Management, L.P. (“ZAM”);
|
|
(ii)
|
PBK
Holdings, Inc. (“PBK”);
|
|
(iii)
|
Philip
B. Korsant; and
|
|
(iv)
|
ZBI
Equities, L.L.C. (“ZBI”).
|
*Attached
as Exhibit A is a copy of an agreement among the Reporting Persons that this
Schedule 13G is being filed on behalf of each of them.
Item
2.(b) Address of Principal Business
Office or, if None, Residence
Ziff
Asset Management, L.P.
283
Greenwich Avenue
Greenwich,
CT 06830
PBK
Holdings, Inc.
283
Greenwich Avenue
Greenwich,
CT 06830
Philip B.
Korsant
283
Greenwich Avenue
Greenwich,
CT 06830
ZBI
Equities, L.L.C.
283
Greenwich Avenue
Greenwich,
CT 06830
Item
2.(c) Citizenship
See Item
4 of the attached cover pages.
Item
2.(d) Title of Class
of Securities
Common
stock, par value $.01 per share (the “Common Shares”)
Item
2.(e) CUSIP
Number
45253H101
Item
3.
Not
applicable as this Schedule 13G is filed pursuant to Rule 13d-1(c).
Item
4.
Ownership
|
(a)
|
Amount beneficially
owned:
|
|
|
See
Item 9 of the attached cover pages.
|
||
|
(b)
|
Percent
of class:
|
|
|
See
Item 11 of the attached cover pages.
|
||
|
(c)
|
Number
of shares as to which such person has:
|
|
|
(i)
|
Sole
power to vote or to direct the vote:
|
|
|
See
Item 5 of the attached cover pages.
|
||
|
(ii)
|
Shared
power to vote or to direct the vote:
|
|
|
See
Item 6 of the attached cover pages.
|
||
|
(iii)
|
Sole
power to dispose or to direct the disposition:
|
|
|
See
Item 7 of the attached cover pages.
|
||
|
(iv)
|
Shared
power to dispose or to direct the disposition:
|
|
|
See
Item 8 of the attached cover pages.
|
||
Philip
B. Korsant shares voting and dispositive power over the shares of Common Stock
that he beneficially owns with ZAM, the owner of record of the shares of Common
Stock. PBK and ZBI also share voting and dispositive power over the
shares of Common Stock that each beneficially owns with ZAM, the
owner of record of the shares of Common Stock.
Item
5.
Ownership of Five Percent or Less of a Class
Not
Applicable.
Item
6.
Ownership of More than Five Percent on Behalf of Another Person
Not
Applicable.
Item
7. Identification
and Classification of the Subsidiary Which Acquired the Security Being Reported
on by the Parent Holding Company
Not
Applicable.
Item
8. Identification
and Classification of Members of the Group
Not
Applicable.
Item
9. Notice of
Dissolution of Group
Not
Applicable.
Item
10. Certification
By
signing below I certify that, to the best of my knowledge and belief, the
securities referred to above were not acquired and are not held for the purpose
of or with the effect of changing or influencing the control of the issuer of
the securities and were not acquired and are not held in connection with or as a
participant in any transaction having that purpose or effect.
SIGNATURE
After
reasonable inquiry and to the best of my knowledge and belief, I certify that
the information set forth in this statement is true, complete and
correct.
Dated: June
30, 2008
|
ZIFF
ASSET MANAGEMENT, L.P.
By: PBK
Holdings, Inc., its general partner
|
|||
|
By:
|
/s/
DAVID GRAY
|
||
|
Name:
|
David
Gray
|
||
|
Title:
|
Vice
President
|
||
|
PBK
HOLDINGS, INC.
|
|||
|
By:
|
/s/
DAVID GRAY
|
||
|
Name:
|
David
Gray
|
||
|
Title:
|
Vice
President
|
||
|
/s/
PHILIP B.
KORSANT
|
||
|
Philip
B. Korsant
|
||
|
|
||
|
ZBI
EQUITIES, L.L.C.
By: PBK
Holdings, Inc., its sole member
|
|||
|
By:
|
/s/
DAVID GRAY
|
||
|
Name:
|
David
Gray
|
||
|
Title:
|
Vice
President
|
||
EXHIBIT
A
The undersigned, Ziff Asset Management,
L.P., a Delaware limited partnership, PBK Holdings, Inc., a Delaware
corporation, Philip B. Korsant, and ZBI Equities, L.L.C., a Delaware limited
liability company, hereby agree and acknowledge that the information required by
this Schedule 13G, to which this Agreement is attached as an exhibit, is filed
on behalf of each of them. The undersigned further agree that any
further amendments or supplements thereto shall also be filed on behalf of each
of them.
Dated: June
30, 2008
|
ZIFF
ASSET MANAGEMENT, L.P.
By: PBK
Holdings, Inc., its general partner
|
|||
|
By:
|
/s/
DAVID GRAY
|
||
|
Name:
|
David
Gray
|
||
|
Title:
|
Vice
President
|
||
|
PBK
HOLDINGS, INC.
|
|||
|
By:
|
/s/
DAVID GRAY
|
||
|
Name:
|
David
Gray
|
||
|
Title:
|
Vice
President
|
||
|
/s/
PHILIP B.
KORSANT
|
||
|
Philip
B. Korsant
|
||
|
|
||
|
ZBI
EQUITIES, L.L.C.
By: PBK
Holdings, Inc., its sole member
|
|||
|
By:
|
/s/
DAVID GRAY
|
||
|
Name:
|
David
Gray
|
||
|
Title:
|
Vice
President
|
||