There is a long list of 190 institutional holders of PRTA within the last two holding periods in our database of 13F filers, so we've sorted through to present to you just the top 50 institutional holders of PRTA by largest to smallest position reported in the institutional investor's latest 13F filing. In the institutional-holders-of-PRTA table below, the initial column indicates the name of each top institutional holder of PRTA, with a link to that fund's top holdings. The next columns indicate the amount of PRTA stock held by each of the institutional holders of PRTA, followed by the PRTA position size held by the institution, and finally the date of the quarterly 13F filing period the holdings data represents for that institution.

Holder	Amount	Position Size ($ in 1000's)	As of
EcoR1 Capital LLC	11,584,280	$420,973	12/31/2023
PRTA	11,584,280	$420,973	12/31/2023
FMR LLC	8,049,796	$292,530	12/31/2023
PRTA	8,049,796	$292,530	12/31/2023
Price T Rowe Associates Inc. MD	4,237,351	$153,986	12/31/2023
PRTA	4,237,351	$153,986	12/31/2023
BlackRock Inc.	3,770,650	$137,025	12/31/2023
PRTA	3,770,650	$137,025	12/31/2023
State Street Corp	2,758,564	$100,246	12/31/2023
PRTA	2,758,564	$100,246	12/31/2023
Wellington Management Group LLP	2,594,102	$94,270	12/31/2023
PRTA	2,594,102	$94,270	12/31/2023
Janus Henderson Group PLC	2,035,984	$73,982	12/31/2023
PRTA	2,035,984	$73,982	12/31/2023
Palo Alto Investors LP	1,660,057	$60,326	12/31/2023
PRTA	1,660,057	$60,326	12/31/2023
First Light Asset Management LLC	1,088,801	$39,567	12/31/2023
PRTA	1,088,801	$39,567	12/31/2023
Vanguard Group Inc.	1,070,555	$38,904	12/31/2023
PRTA	1,070,555	$38,904	12/31/2023
Geode Capital Management LLC	905,125	$32,896	12/31/2023
PRTA	905,125	$32,896	12/31/2023
Dimensional Fund Advisors LP	867,635	$31,533	12/31/2023
PRTA	867,635	$31,533	12/31/2023
Boxer Capital LLC	665,000	$24,166	12/31/2023
PRTA	665,000	$24,166	12/31/2023
Rock Springs Capital Management LP	625,048	$22,714	12/31/2023
PRTA	625,048	$22,714	12/31/2023
Artal Group S.A.	501,360	$18,219	12/31/2023
PRTA	501,360	$18,219	12/31/2023
Morgan Stanley	482,260	$17,525	12/31/2023
PRTA	482,260	$17,525	12/31/2023
Eventide Asset Management LLC	445,155	$16,177	12/31/2023
PRTA	445,155	$16,177	12/31/2023
Granahan Investment Management Inc. MA	417,157	$15,159	12/31/2023
PRTA	417,157	$15,159	12/31/2023
Northern Trust Corp	404,110	$14,685	12/31/2023
PRTA	404,110	$14,685	12/31/2023
Maple Rock Capital Partners Inc.	373,584	$13,576	12/31/2023
PRTA	373,584	$13,576	12/31/2023
JPMorgan Chase & Co.	358,478	$13,027	12/31/2023
PRTA	358,478	$13,027	12/31/2023
Finepoint Capital LP	349,300	$12,694	12/31/2023
PRTA	349,300	$12,694	12/31/2023
Renaissance Technologies LLC	335,800	$12,203	12/31/2023
PRTA	335,800	$12,203	12/31/2023
Goldman Sachs Group Inc.	333,786	$12,130	12/31/2023
PRTA	333,786	$12,130	12/31/2023
Charles Schwab Investment Management Inc.	313,230	$11,383	12/31/2023
PRTA	313,230	$11,383	12/31/2023
Nuveen Asset Management LLC	300,819	$10,932	12/31/2023
PRTA	300,819	$10,932	12/31/2023
UBS Asset Management Americas Inc.	291,867	$10,606	12/31/2023
PRTA	291,867	$10,606	12/31/2023
Bank of America Corp DE	287,355	$10,442	12/31/2023
PRTA	287,355	$10,442	12/31/2023
Prosight Management LP		$10,285	12/31/2023
PRTA	229,539	$8,341	12/31/2023
CALL	53,500	$1,944	12/31/2023
Susquehanna International Group LLP		$10,175	12/31/2023
Call	541,500	$19,678	12/31/2023
Put	295,100	$10,724	12/31/2023
PRTA	33,597	$1,221	12/31/2023
Armistice Capital LLC	278,000	$10,103	12/31/2023
PRTA	278,000	$10,103	12/31/2023
Deep Track Capital LP		$9,085	12/31/2023
Call	500,000	$18,170	12/31/2023
Put	250,000	$9,085	12/31/2023
Rafferty Asset Management LLC	207,419	$7,538	12/31/2023
PRTA	207,419	$7,538	12/31/2023
Qube Research & Technologies Ltd	203,682	$7,402	12/31/2023
PRTA	203,682	$7,402	12/31/2023
PFM Health Sciences LP	189,744	$6,895	12/31/2023
PRTA	189,744	$6,895	12/31/2023
Amundi	166,631	$6,602	12/31/2023
PRTA	166,631	$6,602	12/31/2023
Ikarian Capital LLC		$6,599	12/31/2023
Call	600,000	$21,804	12/31/2023
Put	418,400	$15,205	12/31/2023
Mariner LLC	178,424	$6,484	12/31/2023
PRTA	178,424	$6,484	12/31/2023
Birchview Capital LP	169,574	$6,162	12/31/2023
PRTA	169,574	$6,162	12/31/2023
Connor Clark & Lunn Investment Management Ltd.	155,942	$5,667	12/31/2023
PRTA	155,942	$5,667	12/31/2023
Systematic Financial Management LP	149,759	$5,442	12/31/2023
PRTA	149,759	$5,442	12/31/2023
Two Sigma Advisers LP	146,800	$5,335	12/31/2023
PRTA	146,800	$5,335	12/31/2023
TD Asset Management Inc.	146,538	$5,325	12/31/2023
PRTA	146,538	$5,325	12/31/2023
Barclays PLC	142,607	$5,182	12/31/2023
PRTA	142,607	$5,182	12/31/2023
SG Americas Securities LLC	135,857	$4,937	12/31/2023
PRTA	135,857	$4,937	12/31/2023
UBS Group AG	132,497	$4,815	12/31/2023
PRTA	132,497	$4,815	12/31/2023
AXA S.A.	120,617	$4,383	12/31/2023
PRTA	120,617	$4,383	12/31/2023
Norges Bank	104,564	$3,800	12/31/2023
PRTA	104,564	$3,800	12/31/2023
Jane Street Group LLC		$3,746	12/31/2023
PRTA	185,195	$6,730	12/31/2023
Put	146,800	$5,335	12/31/2023
Call	64,700	$2,351	12/31/2023
Bank of New York Mellon Corp	145,845	$3,613	03/31/2024
PRTA	145,845	$3,613	03/31/2024