<PAGE>
FILED PURSUANT TO RULE 424(b)(3)
SEC FILE NO. 333-45355
IGEN INTERNATIONAL, INC.
PROSPECTUS SUPPLEMENT DATED DECEMBER 8, 1998
to
Prospectus Dated April 15, 1998
This document is a supplement to the prospectus of IGEN International,
Inc., dated April 15, 1998. The purpose of this supplement is to update
information in the prospectus about the offering of up to 5,202,004 shares of
IGEN's common stock by selling securityholders. This supplement should be read
only with the prospectus.
This supplement replaces the Selling Securityholder table on pages 13-14 in
the prospectus. The changes in the new table include adding new selling
securityholders, deleting holders who no longer own the securities, and updating
the amounts of securities that may be sold in the offering or may be held after
the offering. The new table is updated as of October 20, 1998.
Finally, the first sentence of the second paragraph under the heading
"SELLING SECURITYHOLDERS" on page 12 of the prospectus is revised by replacing
"December 31, 1997" with "October 20, 1998." The table and footnotes set forth
on pages 13 and 14 of the Prospectus are deleted and replaced with the
following:
<PAGE>
<TABLE>
<CAPTION>
Number of Percentage
Number of Number of Shares of Shares Owned
Shares Owned Shares Which Owned after After
Prior to May Be Sold in Completion Completion
Selling Stockholder Offering(1) this Offering(2) of Offering(3) of Offering(4)
- ------------------- ----------- ---------------- -------------- --------------
<S> <C> <C> <C> <C>
The Robertson Stephens Black Bear Fund, I, L.P......... 381,686 235,443 146,243 *
The Robertson Stephens Black Bear Fund, II, L.P........ 42,957 30,900 12,057 *
The Robertson Stephens Black Bear Offshore
Fund, L.P.......................................... 164,284 63,984 100,300 *
The Robertson Stephens Black Bear Pacific
Master Fund Unit Trust............................. 60,613 33,813 26,800 *
Credit Suisse First Boston Corporation................. 307,402 208,080 99,322 *
Permal Noscal, Ltd..................................... 312,121 312,121 0 *
Zaxis Partners, L.P.................................... 39,015 39,015 0 *
Sidney Kimmel.......................................... 25,490 25,490 0 *
Pollat, Evans & Co. Inc................................ 8,844 8,844 0 *
Quadra Appreciation Fund, Inc.......................... 3,641 3,641 0 *
Peter W. Branagh & Ramona Y. Branagh Trustee
for the Peter W. Branagh & Ramona Y. Branagh
Revocable Trust, dated March 8, 1993............... 1,040 1,040 0 *
KA Trading L.P......................................... 62,423 62,423 0 *
KA Management Limited.................................. 145,656 145,656 0 *
Putnam Health Sciences Trust........................... 416,161 416,161 0 *
Porter Partners, L.P................................... 167,331 130,051 37,280 *
EDJ Limited............................................ 32,130 26,010 6,120 *
White Rock Capital Offshore, Ltd....................... 373,424 62,424 311,000 2.03%
Quantum Partners LDC................................... 928,600 260,100 668,500 4.36%
Collins Capital Diversified Fund, L.P.................. 92,116 41,616 50,500 *
White Rock Capital Partners, L.P....................... 233,040 104,040 129,000 *
Prism Partners I....................................... 156,060 156,060 0 *
GPZ Trading............................................ 52,020 52,020 0 *
Triton Capital Investments............................. 78,030 78,030 0 *
JMG Capital Partners, L.P.............................. 78,030 78,030 0 *
Manuel Dupkin II....................................... 23,409 23,409 0 *
Stanford Z. Rothschild, Jr. T/U/D 15 Years............. 2,601 2,601 0 *
TOTAL.................................................. 1,587,122
</TABLE>
(1) The number of shares of Common Stock owned by each Selling Securityholder
prior to the Offering includes the shares which may be sold in this
Offering, together with all other shares of Common Stock owned by each
such Selling Securityholder on October 20, 1998.
(2) The number of shares of each Selling Securityholder is based on the
conversion of the Series B Convertible Preferred Stock owned by such
Selling Securityholder on October 20, 1998 and the payment of dividends in
the form of shares by the Company for the full term of the Series B
Convertible Preferred Stock at a rate of $13.96 per Share of Common Stock.
The actual rate of conversion and dividend payment may vary in accordance
with the terms and conditions of the Series B Convertible Preferred Stock.
(3) The number of shares of Common Stock owned by each Selling Securityholder
after completion of the Offering assumes that each Selling Securityholder
sells all of the shares being offered pursuant to this Registration
Statement and that no other shares are bought or sold.
(4) The percentage of shares of Common Stock owned by each Selling
Securityholder after completion of the Offering is based on the number of
shares of Common Stock owned after completion of the Offering, as set
forth in the third column, divided by 15,319,937, which was the number of
shares of Common Stock issued and outstanding on October 20, 1998.
<PAGE>
(*) Indicates less than one percent (1%).
