Phathom Pharmaceuticals, Inc.
US ˙ NasdaqGS ˙ US71722W1071

SecurityPHAT / Phathom Pharmaceuticals, Inc.
InstitutionCitadel Advisors Llc
ManagerKen Griffin
Latest Disclosed Ownership383,058 shares
Latest Disclosed Value $ 4,255,775
Citadel Advisors Llc ownership in PHAT / Phathom Pharmaceuticals, Inc.

On May 15, 2026 - Citadel Advisors Llc filed a 13F-HR form disclosing ownership of 383,058 shares of Phathom Pharmaceuticals, Inc. (US:PHAT) valued at $4,255,774 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 17, 2026 disclosing 311,315 shares of Phathom Pharmaceuticals, Inc.. This represents a change in shares of 23.05% during the quarter. The current value of the position is $3,880,378 USD.

Citadel Advisors Llc has a history of taking positions in derivatives of the underlying security (PHAT) in the form of stock options. The firm currently holds call options representing 515,900 of underlying shares valued at $5,731,649 USD and put options representing 19,200 of underlying shares valued at $213,312 USD .

Note: prior versions of this page mistakenly stated that the share values represented the number of options, not the number of underlying shares. For more information on the data backing these reports, please see the SEC document Frequently Asked Questions About Form 13F.

Institutional Ownership: 13F and NPORT Filings

The Security and Class in the table below are shown exactly as filed by the investor. We do our best to track continuity of investments through acquisitions, and this will be reflected in the table as changes in names. In addition to descriptive data, performance of the investment is shown over time. To calculate quarterly performance, we first calculate cost basis of the shares purchased during the quarter, then use that to calculate gross profit. Quarterly return is Gross Profit / Starting Portfolio value.

Note that cost basis is calculated and stored in thousands, so small quarterly changes in shares frequently result in a cost basis of zero.

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Institutional Put/Call Ratios
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In addition to reporting standard equity and debt issues, institutions with more than 100MM assets under management must also disclose their put and call option holdings. Since put options generally indicate negative sentiment, and call options indicate positive sentiment, we can get a sense of the overall institutional sentiment by plotting the ratio of puts to calls. The chart to the right plots the historical put/call ratio for this instrument.

Using Put/Call Ratio as an indicator of investor sentiment overcomes one of the key deficiencies of using total institutional ownership, which is that a significant amount of assets under management are invested passively to track indices. Passively-managed funds do not typically buy options, so the put/call ratio indicator more closely tracks the sentiment of actively-managed funds.

PHAT / Phathom Pharmaceuticals, Inc. Historical Put/Call Ratio
Disclosed Equity Positions (from 13F/NPORT Filings)
File
Date
Effective
Date
Form Security Class ID Avg Price
Paid (Est)
Reported
Shares
ΔShares ΔShares
(%)
Reported
Value
(x1000)
ΔValue
(%)
Alloc
(%)
ΔAlloc ΔAlloc (%) Cost Basis
(x1000)
Unrealized
Gain/Loss
(x1000)
2026-05-15 2026-03-31 13F PHATHOM PHARMACEUTICALS COM 71722W107 383,058 71,743 23.05 4,256 -17.60 0.0007
2026-02-17 2025-12-31 13F PHATHOM PHARMACEUTICALS COM 71722W107 311,315 -197,405 -38.80 5,165 -13.75 0.0008
2025-11-14 2025-09-30 13F PHATHOM PHARMACEUTICALS COM 71722W107 508,720 508,720 5,988 0.0009
2025-08-14 2025-06-30 13F PHATHOM PHARMACEUTICALS COM 71722W107 0 -179,721 -100.00 0 -100.00
2025-05-15 2025-03-31 13F PHATHOM PHARMACEUTICALS COM 71722W107 179,721 107,714 149.59 1,127 92.81 0.0002
2025-02-14 2024-12-31 13F PHATHOM PHARMACEUTICALS COM 71722W107 72,007 -148,396 -67.33 585 -85.34 0.0001
2024-11-14 2024-09-30 13F PHATHOM PHARMACEUTICALS COM 71722W107 220,403 141,587 179.64 3,985 391.25 0.0008
2024-08-14 2024-06-30 13F PHATHOM PHARMACEUTICALS COM 71722W107 78,816 -46,829 -37.27 812 -39.21 0.0002
2024-05-15 2024-03-31 13F PHATHOM PHARMACEUTICALS COM 71722W107 125,645 114,112 989.44 1,334 1,170.48 0.0003
2024-02-14 2023-12-31 13F PHATHOM PHARMACEUTICALS COM 71722W107 11,533 -264,194 -95.82 105 -96.33 0.0000
2023-11-14 2023-09-30 13F PHATHOM PHARMACEUTICALS COM 71722W107 275,727 258,812 1,530.07 2,859 1,081.40 0.0006
2023-08-14 2023-06-30 13F PHATHOM PHARMACEUTICALS COM 71722W107 16,915 -171,569 -91.03 242 -82.01 0.0001
2023-05-15 2023-03-31 13F PHATHOM PHARMACEUTICALS COM 71722W107 188,484 186,731 10,652.08 1,346 6,978.95 0.0003
2023-02-14 2022-12-31 13F PHATHOM PHARMACEUTICALS COM 71722W107 1,753 1,753 20 0.0000
2022-11-14 2022-09-30 13F PHATHOM PHARMACEUTICALS COM 71722W107 0 -25,012 -100.00 0 -100.00
2022-08-15 2022-06-30 13F PHATHOM PHARMACEUTICALS COM 71722W107 25,012 25,012 212 0.0001
2022-05-16 2022-03-31 13F PHATHOM PHARMACEUTICALS COM 71722W107 0 -11,466 -100.00 0 -100.00
2022-02-14 2021-12-31 13F PHATHOM PHARMACEUTICALS COM 71722W107 11,466 -7,944 -40.93 226 -63.72 0.0000
2021-11-15 2021-09-30 13F PHATHOM PHARMACEUTICALS Cmn 71722W107 19,410 -60,964 -75.85 623 -77.10 0.0001
2021-08-16 2021-06-30 13F PHATHOM PHARMACEUTICALS COM 71722W107 80,374 71,833 841.04 2,721 747.66 0.0006
2021-05-21 2021-03-31 13F/A-1 PHATHOM PHARMACEUTICALS COM 71722W107 8,541 -3,535 -29.27 321 -19.95 0.0001
2021-05-17 2021-03-31 13F PHATHOM PHARMACEUTICALS COM 71722W107 8,541 -3,535 321 0.0001
2021-02-16 2020-12-31 13F PHATHOM PHARMACEUTICALS COM 71722W107 12,076 5,360 79.81 401 63.01 0.0001
2020-11-16 2020-09-30 13F PHATHOM PHARMACEUTICALS COM 71722W107 6,716 6,716 246 0.0001
2020-08-14 2020-06-30 13F PHATHOM PHARMACEUTICALS Cmn 71722W107 0 -11,948 -100.00 0 -100.00
2020-05-15 2020-03-31 13F PHATHOM PHARMACEUTICALS Cmn 71722W107 11,948 11,948 308 0.0001
Disclosed Call Options
File
Date
Effective
Date
Form Security Class ID Opt Avg Share
Price
Shares ΔShares
(%)
Value
(x1000)
ΔValue
(%)
Prior Allocation
(%)
Allocation
(%)
ΔAllocation
(%)
Cost Basis
(x1000)
Profit
(x1000)
Return
(%)
2026-05-15 2026-03-31 13F PHATHOM PHARMACEUTICALS COM Call 515,900 644.44 5,732 398.78 n/a n/a n/a
2026-02-17 2025-12-31 13F PHATHOM PHARMACEUTICALS COM Call 69,300 80.47 1,150 154.77 n/a n/a n/a
2025-11-14 2025-09-30 13F PHATHOM PHARMACEUTICALS COM Call 38,400 -80.90 452 -76.60 n/a n/a n/a
2025-08-14 2025-06-30 13F PHATHOM PHARMACEUTICALS COM Call 201,000 377.43 1,928 632.70 n/a n/a n/a
2025-05-15 2025-03-31 13F PHATHOM PHARMACEUTICALS COM Call 42,100 180.67 264 117.36 n/a n/a n/a
2025-02-14 2024-12-31 13F PHATHOM PHARMACEUTICALS COM Call 15,000 -17.58 122 -63.22 n/a n/a n/a
2024-11-14 2024-09-30 13F PHATHOM PHARMACEUTICALS COM Call 18,200 628.00 329 1,216.00 n/a n/a n/a
2024-08-14 2024-06-30 13F PHATHOM PHARMACEUTICALS COM Call 2,500 -86.56 26 -87.31 n/a n/a n/a
2024-05-15 2024-03-31 13F PHATHOM PHARMACEUTICALS COM Call 18,600 67.57 198 95.05 n/a n/a n/a
2024-02-14 2023-12-31 13F PHATHOM PHARMACEUTICALS COM Call 11,100 -20.14 101 -29.86 n/a n/a n/a
2023-11-14 2023-09-30 13F PHATHOM PHARMACEUTICALS COM Call 13,900 -64.36 144 -74.19 n/a n/a n/a
2023-08-14 2023-06-30 13F PHATHOM PHARMACEUTICALS COM Call 39,000 -10.76 558 78.85 n/a n/a n/a
2023-05-15 2023-03-31 13F PHATHOM PHARMACEUTICALS COM Call 43,700 490.54 312 275.90 n/a n/a n/a
2023-02-14 2022-12-31 13F PHATHOM PHARMACEUTICALS COM Call 7,400 -92.04 83 -91.94 n/a n/a n/a
2022-11-14 2022-09-30 13F PHATHOM PHARMACEUTICALS COM Call 93,000 -3.53 1,030 26.54 n/a n/a n/a
2022-08-15 2022-06-30 13F PHATHOM PHARMACEUTICALS COM Call 96,400 70.92 814 5.99 n/a n/a n/a
2022-05-16 2022-03-31 13F PHATHOM PHARMACEUTICALS COM Call 56,400 768 n/a n/a n/a
2022-02-14 2021-12-31 13F PHATHOM PHARMACEUTICALS Cmn Call 0 -100.00 0 -100.00 n/a n/a n/a
2021-11-15 2021-09-30 13F PHATHOM PHARMACEUTICALS Cmn Call 16,300 523 n/a n/a n/a
Disclosed Put Options
File
Date
Effective
Date
Form Security Class ID Opt Avg Share Price Shares ΔShares
(%)
Value
(x1000)
ΔValue
(%)
Prior Allocation
(%)
Allocation
(%)
ΔAllocation
(%)
Cost Basis
(x1000)
Profit
(x1000)
Return
(%)
2026-05-15 2026-03-31 13F PHATHOM PHARMACEUTICALS COM Put 19,200 -35.14 213 -56.62 n/a n/a n/a
2026-02-17 2025-12-31 13F PHATHOM PHARMACEUTICALS COM Put 29,600 491 n/a n/a n/a
2025-11-14 2025-09-30 13F PHATHOM PHARMACEUTICALS COM Put 0 -100.00 0 -100.00 n/a n/a n/a
2025-08-14 2025-06-30 13F PHATHOM PHARMACEUTICALS COM Put 62,000 68.94 595 158.26 n/a n/a n/a
2025-05-15 2025-03-31 13F PHATHOM PHARMACEUTICALS COM Put 36,700 -58.95 230 -68.28 n/a n/a n/a
2025-02-14 2024-12-31 13F PHATHOM PHARMACEUTICALS COM Put 89,400 620.97 726 223.66 n/a n/a n/a
2024-11-14 2024-09-30 13F PHATHOM PHARMACEUTICALS COM Put 12,400 163.83 224 366.67 n/a n/a n/a
2024-08-14 2024-06-30 13F PHATHOM PHARMACEUTICALS COM Put 4,700 -47.78 48 -49.47 n/a n/a n/a
2024-05-15 2024-03-31 13F PHATHOM PHARMACEUTICALS COM Put 9,000 32.35 96 53.23 n/a n/a n/a
2024-02-14 2023-12-31 13F PHATHOM PHARMACEUTICALS COM Put 6,800 142.86 62 113.79 n/a n/a n/a
2023-11-14 2023-09-30 13F PHATHOM PHARMACEUTICALS COM Put 2,800 -47.17 29 -61.33 n/a n/a n/a
2023-08-14 2023-06-30 13F PHATHOM PHARMACEUTICALS COM Put 5,300 178.95 76 476.92 n/a n/a n/a
2023-05-15 2023-03-31 13F PHATHOM PHARMACEUTICALS COM Put 1,900 -81.90 14 -88.89 n/a n/a n/a
2023-02-14 2022-12-31 13F PHATHOM PHARMACEUTICALS COM Put 10,500 118 n/a n/a n/a
Legend
Shares
The total number of shares held by the institution at the end of the reporting period (the effective date). This is provided in the filing.
Value
The total value of the shares as of the effective date. This is provided in the filing.
Avg. Share Price
The weighted average share price of the shares held by the institution. We use FIFO accounting to determine this price
Class
This is the security class as indicated by the filer. There are a variety of values for this field. Common values include "EC" = equity common, "EP" - equity preferred
Allocation (%)
The percent of the institution's portfolio that this position represents. This is provided in NPORT filings. For 13F filings, we calculate it.
Change in Allocation
The change in allocation from the prior reporting period. This is calculated as current allocation - prior allocation.
Change in Allocation (%)
The percent change in allocation from the prior reporting period. This is calculated as (current allocation - prior allocation) / prior allocation.
Cost Basis
The total cost of the shares held. This is calculated as reported shares * avg. share price
Unrealized Gain/Loss
This is the market value of the position as of the effective date minus the cost basis.