Altimmune reports Schedule 13G ownership by TCG Crossover funds and Chen Yu. The filing lists aggregate shared voting and dispositive power of 10,000,000 shares for each TCG Crossover fund entity (reported as 5.0% of the class) and reports 20,000,000 shares attributable to Chen Yu (reported as 9.8% of the class). The filing states 194,199,358 shares outstanding as of April 24, 2026 following an underwritten offering and references an additional 10,000,000 shares issuable upon exercise of Common Warrants held by the TCG Crossover entities.
Positive
None.
Negative
None.
Insights
Holdings approach a single‑digit ownership cap under warrant limits.
The Schedule 13G shows each TCG fund reporting 10,000,000 shared voting/dispositive shares and Chen Yu reporting 20,000,000 aggregated. The Common Warrants include a Beneficial Ownership Limitation preventing exercise beyond 9.99%.
The operative facts to watch are whether warrant exercises are constrained by the 9.99% limit and whether subsequent filings adjust percentages after any future conversions or offerings.
Positions reflect passive reporting post‑offering rather than active control changes.
The filing ties the ownership base to 194,199,358 outstanding shares as of April 24, 2026 and notes 5,000,000 warrants per fund (aggregate 10,000,000 issuable). Reported percentages are 5.0% for each fund and 9.8% for Chen Yu on the stated base.
Subsequent Schedule 13 filings would show any shifts from passive to active ownership; until then, this filing documents current beneficial‑ownership positions only.
Key Figures
Shares outstanding:194,199,358 sharesWarrants issuable (aggregate for TCG funds):10,000,000 sharesTCG Crossover shared holdings (per fund):10,000,000 shares+3 more
6 metrics
Shares outstanding194,199,358 sharesoutstanding as of April 24, 2026 following the Offering
Warrants issuable (aggregate for TCG funds)10,000,000 sharesshares issuable upon exercise of Common Warrants held by TCG Crossover II and III
TCG Crossover shared holdings (per fund)10,000,000 sharesshared voting and dispositive power reported for each TCG Crossover entity
Chen Yu attributable shares20,000,000 sharesaggregated across TCG Crossover II and III holdings and warrants
Chen Yu percent of class9.8%based on 204,199,358 shares of Common Stock per filing comment
Warrant ownership cap9.99%Beneficial Ownership Limitation in the Common Warrants
Key Terms
Beneficial Ownership Limitation, Common Warrants, Rule 13d-1(k)(1), Shared dispositive power
4 terms
Beneficial Ownership Limitationregulatory
"prohibits the exercise of the Common Warrants to the extent that doing so would result"
A beneficial ownership limitation is a rule that caps the percentage of a company’s shares an investor can be treated as owning or controlling for voting, regulatory or tax purposes. It matters to investors because it can restrict how many shares a person or group can buy or vote, affect takeover chances, and influence share liquidity and value — like a speed limit that prevents any single driver from taking over the whole road.
Common Warrantsfinancial
"5,000,000 shares of Common Stock issuable upon exercise of Common Warrants"
A common warrant is a tradable instrument that gives its holder the right to buy a company’s common shares at a fixed price within a set time period, similar to a coupon that can be redeemed later to purchase stock. Investors care because exercising warrants can boost potential gains if the stock rises, but it can also dilute existing shareholders by increasing the number of shares outstanding, which can lower per-share value.
Rule 13d-1(k)(1)regulatory
"jointly in accordance with the provisions of Rule 13d-1(k)(1)"
Shared dispositive powerfinancial
"Shared Dispositive Power 10,000,000.00"
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
SCHEDULE 13G
UNDER THE SECURITIES EXCHANGE ACT OF 1934
Altimmune, Inc.
(Name of Issuer)
Common Stock, par value $0.0001 per share
(Title of Class of Securities)
02155H200
(CUSIP Number)
04/24/2026
(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)
Rule 13d-1(c)
Rule 13d-1(d)
schemaVersion:
SCHEDULE 13G
CUSIP Number(s):
02155H200
1
Names of Reporting Persons
TCG Crossover GP II, LLC
2
Check the appropriate box if a member of a Group (see instructions)
(a)
(b)
3
Sec Use Only
4
Citizenship or Place of Organization
DELAWARE
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
0.00
6
Shared Voting Power
10,000,000.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
10,000,000.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
10,000,000.00
10
Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
11
Percent of class represented by amount in row (9)
5.0 %
12
Type of Reporting Person (See Instructions)
OO
Comment for Type of Reporting Person: Consists of (i) 5,000,000 shares of Common Stock and (ii) 5,000,000 shares of Common Stock issuable upon exercise of Common Warrants (the Common Warrants) held of record by TCG Crossover II (as defined in Item 2(a) below). TCG Crossover GP II (as defined in Item 2(a) below) is the general partner of TCG Crossover II and may be deemed to have voting, investment, and dispositive power with respect to these securities. Chen Yu is the sole managing member of TCG Crossover GP II and may be deemed to share voting, investment and dispositive power with respect to these securities. The Common Warrants contain a provision which prohibits the exercise of the Common Warrants to the extent that doing so would result in the holder of the Common Warrants (together with the holder's affiliates and any other persons acting as a group together with the holder or any of the holder's affiliates) beneficially owning more than 9.99 percent of the shares of Common Stock then outstanding immediately after giving effect to such exercise (the Beneficial Ownership Limitation). As of the date of this filing, the Reporting Persons (as defined in Item 2(a) below) hold less than the Beneficial Ownership Limitation in the aggregate.
Based on 199,199,358 shares of Common Stock, as follows: (a) 194,199,358 outstanding as of April 24, 2026, following the underwritten offering that closed on April 24, 2026 (the Offering), as reported by the Issuer (as defined in Item 1(a) below) in its prospectus filed with the United States Securities and Exchange Commission (the Commission) on April 24, 2026 (the Prospectus), plus (b) 5,000,000 shares of Common Stock issuable upon exercise of Common Warrants held of record by TCG Crossover II.
SCHEDULE 13G
CUSIP Number(s):
02155H200
1
Names of Reporting Persons
TCG Crossover Fund II, L.P.
2
Check the appropriate box if a member of a Group (see instructions)
(a)
(b)
3
Sec Use Only
4
Citizenship or Place of Organization
DELAWARE
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
0.00
6
Shared Voting Power
10,000,000.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
10,000,000.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
10,000,000.00
10
Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
11
Percent of class represented by amount in row (9)
5.0 %
12
Type of Reporting Person (See Instructions)
PN
Comment for Type of Reporting Person: Consists of (i) 5,000,000 shares of Common Stock and (ii) 5,000,000 shares of Common Stock issuable upon exercise of Common Warrants held of record by TCG Crossover II. TCG Crossover GP II is the general partner of TCG Crossover II and may be deemed to have voting, investment, and dispositive power with respect to these securities. Chen Yu is the sole managing member of TCG Crossover GP II and may be deemed to share voting, investment and dispositive power with respect to these securities. The Common Warrants contain a provision which prohibits the exercise of the Common Warrants due to the Beneficial Ownership Limitation. As of the date of this filing, the Reporting Persons hold less than the Beneficial Ownership Limitation in the aggregate.
Based on 199,199,358 shares of Common Stock, as follows: (a) 194,199,358 outstanding as of April 24, 2026, following the Offering, as reported by the Issuer in the Prospectus, plus (b) 5,000,000 shares of Common Stock issuable upon exercise of Common Warrants held of record by TCG Crossover II.
SCHEDULE 13G
CUSIP Number(s):
02155H200
1
Names of Reporting Persons
TCG Crossover GP III, LLC
2
Check the appropriate box if a member of a Group (see instructions)
(a)
(b)
3
Sec Use Only
4
Citizenship or Place of Organization
DELAWARE
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
0.00
6
Shared Voting Power
10,000,000.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
10,000,000.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
10,000,000.00
10
Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
11
Percent of class represented by amount in row (9)
5.0 %
12
Type of Reporting Person (See Instructions)
OO
Comment for Type of Reporting Person: Consists of (i) 5,000,000 shares of Common Stock and (ii) 5,000,000 shares of Common Stock issuable upon exercise of Common Warrants held of record by TCG Crossover III (as defined in Item 2(a) below). TCG Crossover GP III (as defined in Item 2(a) below) is the general partner of TCG Crossover III and may be deemed to have voting, investment, and dispositive power with respect to these securities. Chen Yu is the sole managing member of TCG Crossover GP III and may be deemed to share voting, investment and dispositive power with respect to these securities. The Common Warrants contain a provision which prohibits the exercise of the Common Warrants due to the Beneficial Ownership Limitation. As of the date of this filing, the Reporting Persons hold less than the Beneficial Ownership Limitation in the aggregate.
Based on 199,199,358 shares of Common Stock, as follows: (a) 194,199,358 outstanding as of April 24, 2026, following the Offering, as reported by the Issuer in the Prospectus, plus (b) 5,000,000 shares of Common Stock issuable upon exercise of Common Warrants held of record by TCG Crossover III.
SCHEDULE 13G
CUSIP Number(s):
02155H200
1
Names of Reporting Persons
TCG Crossover Fund III, L.P.
2
Check the appropriate box if a member of a Group (see instructions)
(a)
(b)
3
Sec Use Only
4
Citizenship or Place of Organization
DELAWARE
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
0.00
6
Shared Voting Power
10,000,000.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
10,000,000.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
10,000,000.00
10
Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
11
Percent of class represented by amount in row (9)
5.0 %
12
Type of Reporting Person (See Instructions)
PN
Comment for Type of Reporting Person: Consists of (i) 5,000,000 shares of Common Stock and (ii) 5,000,000 shares of Common Stock issuable upon exercise of Common Warrants held of record by TCG Crossover III. TCG Crossover GP III is the general partner of TCG Crossover III and may be deemed to have voting, investment, and dispositive power with respect to these securities. Chen Yu is the sole managing member of TCG Crossover GP III and may be deemed to share voting, investment and dispositive power with respect to these securities. The Common Warrants contain a provision which prohibits the exercise of the Common Warrants due to the Beneficial Ownership Limitation. As of the date of this filing, the Reporting Persons hold less than the Beneficial Ownership Limitation in the aggregate.
Based on 199,199,358 shares of Common Stock, as follows: (a) 194,199,358 outstanding as of April 24, 2026, following the Offering, as reported by the Issuer in the Prospectus, plus (b) 5,000,000 shares of Common Stock issuable upon exercise of Common Warrants held of record by TCG Crossover III.
SCHEDULE 13G
CUSIP Number(s):
02155H200
1
Names of Reporting Persons
Chen Yu
2
Check the appropriate box if a member of a Group (see instructions)
(a)
(b)
3
Sec Use Only
4
Citizenship or Place of Organization
UNITED STATES
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
0.00
6
Shared Voting Power
20,000,000.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
20,000,000.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
20,000,000.00
10
Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
11
Percent of class represented by amount in row (9)
9.8 %
12
Type of Reporting Person (See Instructions)
IN
Comment for Type of Reporting Person: Consists of (i) 5,000,000 shares of Common Stock held of record by TCG Crossover II, (ii) 5,000,000 shares of Common Stock issuable upon exercise of Common Warrants held of record by TCG Crossover II, (iii) 5,000,000 shares of Common Stock held of record by TCG Crossover III, and (iv) 5,000,000 shares of Common Stock issuable upon exercise of Common Warrants held of record by TCG Crossover III. TCG Crossover GP II is the general partner of TCG Crossover II and may be deemed to have voting, investment, and dispositive power with respect to the securities held of record by TCG Crossover II. TCG Crossover GP III is the general partner of TCG Crossover III and may be deemed to have voting, investment, and dispositive power with respect to the securities held of record by TCG Crossover III. Chen Yu is the sole managing member of each of TCG Crossover GP II and TCG Crossover GP III and may be deemed to share voting, investment and dispositive power with respect to the securities held of record by TCG Crossover II and TCG Crossover III. The Common Warrants contain a provision which prohibits the exercise of the Common Warrants due to the Beneficial Ownership Limitation. As of the date of this filing, the Reporting Persons hold less than the Beneficial Ownership Limitation in the aggregate.
Based on 204,199,358 shares of Common Stock, as follows: (a) 194,199,358 outstanding as of April 24, 2026, following the Offering, as reported by the Issuer in the Prospectus, plus (b) an aggregate of 10,000,000 shares of Common Stock issuable upon exercise of Common Warrants held of record by TCG Crossover II and TCG Crossover III.
SCHEDULE 13G
Item 1.
(a)
Name of issuer:
Altimmune, Inc.
(b)
Address of issuer's principal executive offices:
910 Clopper Road, Suite 201S, Gaithersburg, MD 20878
Item 2.
(a)
Name of person filing:
This joint statement on Schedule 13G is being filed by TCG Crossover Fund II, L.P. (TCG Crossover II), TCG Crossover GP II, LLC (TCG Crossover GP II), TCG Crossover Fund III, L.P. (TCG Crossover III) and TCG Crossover GP III, LLC (TCG Crossover GP III and together with TCG Crossover II, TCG Crossover GP II and TCG Crossover III, the Reporting Entities) and Chen Yu (the Reporting Individual). The Reporting Entities and the Reporting Individual are collectively referred to as the Reporting Persons. The Reporting Persons expressly disclaim status as a group for purposes of this Schedule 13G. The agreement among the Reporting Persons to file jointly in accordance with the provisions of Rule 13d-1(k)(1) under the Act is attached to this Statement as Exhibit 1. Other than those securities reported herein as being held directly by such Reporting Person, each Reporting Person disclaims beneficial ownership of all securities reported in this Statement except to the extent of such Reporting Person's pecuniary interest therein.
(b)
Address or principal business office or, if none, residence:
The address of the principal business office of each Reporting Person is 245 Lytton Ave., Suite 350, Palo Alto, CA 94301.
(c)
Citizenship:
TCG Crossover GP II and TCG Crossover GP III are each a limited liability company organized under the laws of the State of Delaware. TCG Crossover II and TCG Crossover III are each a limited partnership organized under the laws of the State of Delaware. The Reporting Individual is a citizen of the United States of America.
(d)
Title of class of securities:
Common Stock, par value $0.0001 per share
(e)
CUSIP Number(s):
02155H200
Item 3.
If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)
Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)
Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)
Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)
Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)
An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)
An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)
A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)
A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)
A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)
A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J),
please specify the type of institution:
(k)
Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.
Ownership
(a)
Amount beneficially owned:
See Row 9 of the cover page for each Reporting Person and the corresponding comments.
(b)
Percent of class:
See Row 11 of the cover page for each Reporting Person and the corresponding comments.
(c)
Number of shares as to which the person has:
(i) Sole power to vote or to direct the vote:
See Row 5 of the cover page for each Reporting Person and the corresponding comments.
(ii) Shared power to vote or to direct the vote:
See Row 6 of the cover page for each Reporting Person and the corresponding comments.
(iii) Sole power to dispose or to direct the disposition of:
See Row 7 of the cover page for each Reporting Person and the corresponding comments.
(iv) Shared power to dispose or to direct the disposition of:
See Row 8 of the cover page for each Reporting Person and the corresponding comments.
Item 5.
Ownership of 5 Percent or Less of a Class.
Not Applicable
Item 6.
Ownership of more than 5 Percent on Behalf of Another Person.
If any other person is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, such securities, a statement to that effect should be included in response to this item and, if such interest relates to more than 5 percent of the class, such person should be identified. A listing of the shareholders of an investment company registered under the Investment Company Act of 1940 or the beneficiaries of employee benefit plan, pension fund or endowment fund is not required.
Under certain circumstances set forth in the limited partnership agreements of TCG Crossover II and TCG Crossover III and the limited liability company agreements of TCG Crossover GP II and TCG Crossover GP III, the general and limited partners or members, as the case may be, of each of such entities may be deemed to have the right to receive dividends from, or the proceeds from, the sale of securities of the Issuer owned by each such entity of which they are a partner or member, as the case may be.
Item 7.
Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
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.
Certifications:
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, other than activities solely in connection with a nomination under ?? 240.14a-11.
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.
What stake do TCG Crossover funds report in Altimmune (ALT)?
TCG Crossover entities report 10,000,000 shares each, shown as 5.0% of the class. The filing attributes these amounts to holdings plus warrants exercisable into common stock and references the same 5.0% percent figure for each fund.
How much of Altimmune does Chen Yu beneficially own according to the 13G?
Chen Yu is reported with 20,000,000 shares, equal to 9.8% of the class. The filing aggregates holdings and warrant issuable shares across the TCG entities to arrive at the 20,000,000 figure.
What share count is the filing using as the ownership denominator for ALT?
The filing uses 194,199,358 shares outstanding as of April 24, 2026 after the underwritten offering and notes an aggregate of 10,000,000 shares issuable on warrants in its calculations.
Do the Common Warrants allow full exercise into Altimmune shares?
No. The Common Warrants include a Beneficial Ownership Limitation that prevents exercise if it would cause beneficial ownership to exceed 9.99% of outstanding shares, as described in the filing.
Does the 13G indicate active group status between the Reporting Persons?
The Reporting Persons expressly disclaim status as a group while filing jointly under Rule 13d-1(k)(1), per the joint filing agreement attached as Exhibit 1.
