Question 1

Does RTW Investments own CSTL stock?

Accepted Answer

Yes. As of its Q2 2026 13F, RTW Investments holds 2,778,335 shares of CSTL (Castle Biosciences), worth $66.3M.

Question 2

How many shares of CSTL does RTW Investments own?

Accepted Answer

As of its Q2 2026 13F, RTW Investments holds 2,778,335 shares of CSTL (Castle Biosciences).

Question 3

What is RTW Investments' CSTL position worth?

Accepted Answer

As of its Q2 2026 13F, RTW Investments' CSTL position is worth $66.3M.

Question 4

Is RTW Investments buying or selling CSTL?

Accepted Answer

In Q2 2026, RTW Investments increased its CSTL position by 20,000 shares (+0.7%).

Question 5

When did RTW Investments first buy CSTL?

Accepted Answer

RTW Investments already held CSTL in its Q3 2019 13F, the earliest on record, and has listed it in 18 quarterly 13F filings.

Quarter	Action	Shares	Change	Value	Weight	Price	Conviction
2026-Q2 Latest	Increased	2.8M	+0.7%	$66.3M	0.6%	$23.85	42
2026-Q1	Increased	2.8M	+30.4%	$67.7M	0.7%	$27.57	53
2025-Q4	New	2.1M	—	$82.3M	0.8%	$39.31	58