undamentalytics Newsletter

Ra Capital Management, L.P.: insider trades

Director, 10% owner, Other at 19 companies we cover. 18 open-market purchases and 11 sales not made under a pre-set plan, reported from September 19, 2016 to September 21, 2026.

Would copying Ra Capital Management, L.P.’s purchases have beaten the S&P 500?

Too few purchases to judge. Only 14 purchases have 12 months of prices after the report; we judge insiders once they have 20. The figures below can swing a long way on a handful of trades. Buying each purchase the day after it was reported, an equal amount each, and holding it 12 months or until they reported a sale would have turned $10,000 on November 16, 2017 into $1,992 by November 2, 2026, −16.5% a year. The copy held shares only 86% of the time, so the fair comparison is the S&P 500 on those same days with Treasury bills otherwise: $38,162, +16.2% a year (the S&P 500 held throughout made $33,572, +14.5% a year). Beta against the index was 0.89. Twelve months after each report, the average purchase was −21.9% against the S&P 500 (median −36.9%), and 29% beat it. Measured from the trade date, the insider’s own timing, the average was −16.0%. After their sales, the shares moved −47.5% against the index over 12 months on average (a negative figure means selling was the right call); 100% trailed it.

With 296 insiders tested, some will look skilled or unskilled by chance alone: when we replaced each insider’s stocks with random companies bought on the same days, about 5.7 cleared the bar ahead and 23.3 behind. One record on its own proves little.

$0$20.0k$40.0k 20172019202120232025 $38.2k$33.6k$2.0k
Copying Ra Capital Management, L.P.S&P 500, same days investedS&P 500, held throughout $10,000 copying Ra Capital Management, L.P.’s open-market purchases from November 16, 2017, before costs and taxes, marked weekly. Each purchase gets the same starting stake, bought at the close of the first trading day after the report and sold 12 months later or the day after a reported sale of that stock; uninvested money earns the Treasury bill rate. “Same days invested” holds the S&P 500 only on the days the copy held shares, Treasury bills otherwise.
Return a year, copying
−16.5%
S&P 500, same days invested
+16.2% (held throughout +14.5%)
Time in shares
86%
Sharpe ratio (S&P 500)
0.02 (0.67)
Biggest drop (S&P 500)
−94% (−34%)
Market sensitivity (beta)
0.89
Purchases copied
17

Trade by trade

Ra Capital Management, L.P.: trades against the S&P 500 afterwards
MeasuredTrades countedAverage vs S&P 500MedianWent the right wayYearst-statisticp-valueEvidence
Purchases, 3 months after the report 17 −19.7% −23.1% 24% 9 −1.03 0.33 No reliable evidence
Purchases, 6 months after the report 16 −14.5% −12.5% 38% 9 −0.80 0.45 No reliable evidence
Purchases, 12 months after the report 14 −21.9% −36.9% 29% 8 −1.33 0.23 No reliable evidence
Purchases, 12 months after the trade 14 −16.0% −26.4% 29% 8 −0.94 0.38 No reliable evidence
Sales, 3 months after the report 7 −4.1% −7.2% 57% 4 −0.09 0.93 No reliable evidence
Sales, 12 months after the report 4 −47.5% −41.1% 100% 3 — — Not enough years
Sales, 12 months after the trade 4 −52.9% −51.1% 100% 3 — — Not enough years

“Average vs S&P 500” is the stock’s return including dividends minus the index’s over the same dates, from the close on the first trading day after the report, or from the close on the trade date. Only windows that have finished are counted. For sales, a negative figure means the stock lagged after it was sold, so selling was the right call (green). “Went the right way” is the share of purchases that beat the index, or of sales that trailed it. The t-statistic uses one average per year of reports, because one person’s trades bunch into the same stock and weeks, and needs trades in at least four different years; the p-value comes from the t distribution with that number of years (with four years, a t of 2 has p = 0.14). “Some evidence” means p under 5%, “strong evidence” p under 1% over at least six years.

Companies traded

CompanyTitle on the latest filingPurchasesSalesFirst reportLatest report
Wave Life Sciences, Inc. WVE —30November 15, 2017March 30, 2026
Vor Biopharma Inc. VOR —03October 27, 2025April 21, 2026
Werewolf Therapeutics, Inc. HOWL —03May 12, 2026June 22, 2026
Rhythm Pharmaceuticals, Inc. RYTM —02July 2, 2020December 4, 2020
Fulcrum Therapeutics, Inc. FULC —20December 16, 2022January 24, 2023
ARS Pharmaceuticals, Inc. SPRY —20August 31, 2023March 27, 2024
Sionna Therapeutics, Inc. SION —02November 19, 2025September 21, 2026
Aclaris Therapeutics, Inc. ACRS —01September 19, 2016September 19, 2016
Kala BIO, Inc. KALA —10October 5, 2018October 5, 2018
Phathom Pharmaceuticals, Inc. PHAT —10March 31, 2020March 31, 2020
Cytek Biosciences, Inc. CTKB —10February 16, 2022February 16, 2022
Enliven Therapeutics, Inc. ELVN —10January 5, 2023January 5, 2023
Black Diamond Therapeutics, Inc. BDTX —10July 7, 2023July 7, 2023
Acumen Pharmaceuticals, Inc. ABOS —10July 25, 2023July 25, 2023
Nkarta, Inc. NKTX —10March 29, 2024March 29, 2024
Tyra Biosciences, Inc. TYRA —10June 16, 2025June 16, 2025
Mineralys Therapeutics, Inc. MLYS —10September 8, 2025September 8, 2025
Bicara Therapeutics Inc. BCAX —10March 2, 2026March 2, 2026
Artiva Biotherapeutics, Inc. ARTV —10June 29, 2026June 29, 2026

Trades and what followed

Moves are against the S&P 500; green means the trade went the insider’s way.

ReportedTradedCompanyTradeValue3 months after report12 months after report12 months after trade
September 21, 2026September 17, 2026 SION Sale $21,835,018 not yetnot yetnot yet
June 29, 2026June 25, 2026 ARTV Purchase $292,126 −30.1%not yetnot yet
June 22, 2026June 17, 2026 HOWL Sale $145,919 not yetnot yetnot yet
June 16, 2026June 12, 2026 HOWL Sale $173,758 not yetnot yetnot yet
May 12, 2026May 8, 2026 HOWL Sale $390,688 not yetnot yetnot yet
April 21, 2026April 17, 2026 VOR Sale $10,174,788 +19.8%not yetnot yet
April 15, 2026April 13, 2026 VOR Sale $11,883,340 +14.6%not yetnot yet
March 30, 2026March 26, 2026 WVE Purchase $54,624,378 −34.4%not yetnot yet
March 2, 2026February 26, 2026 BCAX Purchase $4,800,000 −2.4%not yetnot yet
November 19, 2025November 17, 2025 SION Sale $5,500,158 −9.8%not yetnot yet
October 27, 2025October 23, 2025 VOR Sale $6,204,863 −49.4%−35.5%−49.1%
September 8, 2025September 4, 2025 MLYS Purchase $29,999,985 −6.2%−41.7%−34.8%
June 16, 2025June 12, 2025 TYRA Purchase $1,664,700 +16.1%+168.6%+149.9%
March 29, 2024March 27, 2024 NKTX Purchase $30,000,000 −50.7%−91.8%−91.7%
March 27, 2024March 25, 2024 SPRY Purchase $13,289,410 −21.1%+14.0%+27.8%
August 31, 2023August 29, 2023 SPRY Purchase $23,250,000 −32.5%+44.0%+57.0%
July 25, 2023July 21, 2023 ABOS Purchase $39,999,998 −45.1%−72.2%−76.3%
July 7, 2023July 5, 2023 BDTX Purchase $4,679,250 not yetnot yetnot yet
January 24, 2023January 20, 2023 FULC Purchase $24,999,988 −81.3%−69.6%−71.1%
January 5, 2023January 3, 2023 ELVN Purchase $2,517,188 +4.3%−51.3%−32.0%
December 16, 2022December 14, 2022 FULC Purchase $13,076,472 −48.3%−32.0%−20.8%
February 16, 2022February 14, 2022 CTKB Purchase $7,427,905 −23.1%−18.8%−13.4%
December 4, 2020December 2, 2020 RYTM Sale $7,029,653 −16.5%−94.2%−97.7%
July 2, 2020June 30, 2020 RYTM Sale $2,902,515 −7.2%−46.6%−53.1%
March 31, 2020March 27, 2020 PHAT Purchase $1,489,230 +1.8%−18.0%−11.6%
January 28, 2019January 24, 2019 WVE Purchase $10,000,004 −35.0%−105.1%−106.0%
October 5, 2018October 3, 2018 KALA Purchase $19,999,996 −16.9%−60.3%−51.5%
November 15, 2017November 13, 2017 WVE Purchase $9,881,552 +69.9%+27.7%+49.9%
September 19, 2016September 15, 2016 ACRS Sale $12,713,534 +19.9%−13.5%−11.7%

Open-market purchases and sales of at least $10,000 in companies we cover, from SEC Form 4 filings; sales made under a pre-set Rule 10b5-1 plan are not shown. “Not yet” means the window has not finished or the share price was under $5 at entry. These are the shares’ moves after each trade: they say nothing about why Ra Capital Management, L.P. traded and do not suggest the use of non-public information. How every insider compares · the insider trading backtest.