Alector, Inc. — Director's Dealing 2019

Aug 9, 2019

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: Alector, Inc. (ALEC)
CIK: 0001653087
Period of Report: 2019-08-07

Reporting Person: ORBIMED ADVISORS LLC (10% Owner)
Reporting Person: OrbiMed Capital GP IV LLC (10% Owner)
Reporting Person: ORBIMED CAPITAL LLC (10% Owner)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2019-08-07	Common Stock	S	492364	$17.90	Disposed	9272225	Indirect
2019-08-07	Common Stock	S	157636	$17.90	Disposed	2968604	Indirect

Holdings (Non-Derivative)

Security	Shares	Ownership
Common Stock	203200	Indirect

Footnotes

F1: These shares of the Issuer's common stock ("Shares") were sold in a block order at a price of $17.90.

F2: The Shares are held of record by OrbiMed Private Investments IV-AL, LP ("OrbiMed IV-AL"). OrbiMed Capital GP IV LLC ("OrbiMed GP"), is the general partner of OrbiMed IV-AL. OrbiMed Advisors LLC ("OrbiMed Advisors"), a registered adviser under the Investment Advisers Act of 1940, as amended, is the managing member of OrbiMed GP. By virtue of such relationships, OrbiMed GP and OrbiMed Advisors may be deemed to have voting and investment power over the securities held by OrbiMed IV-AL and as a result may be deemed to have beneficial ownership over such securities.

F3: Each of OrbiMed GP, OrbiMed Capital LLC ("OrbiMed Capital") and OrbiMed Advisors disclaims beneficial ownership of the securities reported herein for purposes of Rule 16a-1(a) under the Securities Exchange Act of 1934, as amended (the "Exchange Act"), except to the extent of its pecuniary interest therein, if any. This report on Form 4 shall not be deemed an admission that any of the Reporting Persons is a beneficial owner of such securities for the purpose of Section 16 of the Exchange Act, or for any other purpose.

F4: The Shares are held of record by OrbiMed Private Investments IV-AL (Feeder), LP ("OrbiMed IV-AL (Feeder)"). OrbiMed GP is the general partner of OrbiMed IV-AL (Feeder). OrbiMed Advisors, a registered adviser under the Investment Advisers Act of 1940, as amended, is the managing member of OrbiMed GP. By virtue of such relationships, OrbiMed GP and OrbiMed Advisors may be deemed to have voting and investment power over the securities held by OrbiMed IV-AL (Feeder) and as a result may be deemed to have beneficial ownership over such securities.

F5: The Shares are held of record by OrbiMed Partners Master Fund Limited ("OPM"). OrbiMed Capital, a registered investment adviser under the Investment Advisers Act, acts as the investment advisor to OPM. By virtue of such relationships, OrbiMed Capital may be deemed to have voting and investment power over the securities held by OPM and as a result may be deemed to have beneficial ownership over such securities.

F6: Amounts reflect a correction to the allocation of the Shares held by each of OrbiMed IV-AL and OrbiMed IV-AL (Feeder).